Just bought myself a Corsair K70 LUX RGB. It is a well built board that has a USB port (it's actually a pass through which can be a bit more compatible with things like an external HDD etc.).
The lighting is fun to play with. If you don't care about that, you can save a few bucks and get the non-RGB version (double check if that comes with the USB port though, not sure).
The build quality is nice. I just decided to replace my 10 year old Deck 82 with it. I'm pretty happy so far.
I'm surprised you still have the G15. I had the orriginal G15 and after about 3 years, it would start randomly disconnecting from my machine. I had to retire it. Going from a rubber membrane keyboard to a nice mechanical board is a huge upgrade in my opinion but take the time to go to a retail place that sells them and see if you can feel the different key switches to see what you prefer the feel of.
How much do you wish to spend, first of all? Next, did you ever use the extra G-Key macro keys and would you like them again? All of the suggestions I'm going to provide offer mechanical keys which will feel different/better than typing on an old membrane G15, plus individual-key RGB backlighting that allows you to pick any color for any key or even crazy patterns should you wish it! I'll also stick to full-sized keyboards for now with numpads etc... but if you would like a compact and/or "tenkeyless" variety they're out there too just let me know.
Next, as a former G15 owner, I know how useful the old thing could be - the screen was a lifesaver backwhen with no secondary display. Here are some relatively comparable upgraded variants...
Logitech G910 Orion Spectrum - http://gaming.logitech.com/en-us/product/g910-orion-spectrum-rgb-gaming-keyboard - This is Logitech's successor to the G15 series. Note that the Orion Spectrum is the newer, upgraded version compared to the Orion Spark, which has kind of wonky angled keytops and a funny font. The G910 has some extra macro keys and dedicated but compact media/volume keys, has well-regarded mechanical keys that are comparable to CherryMX Brown, and familiar yet upgraded Logitech driver software that is useful and doesn't require a lot of installed nonsense. They also have a "Tenkeyless" smaller version called the "Pro", http://gaming.logitech.com/en-us/product/pro-gaming-keyboard . The only downside compared to what you mentioned is no USB hub/pass throughs on these. Its up to you to decide how much it matters.
Roccat Ryos MK FX - - http://www.roccat.org/en-US/Products/Gaming-Keyboards/Ryos-Series/Ryos-MK-FX/ - Another option, Roccat has Cherry MX Brown switches and some unique features like the "thumbster" keys and the use of CapsLock to be rebound to sort of an additional function keys. It lacks the USB passthrough and the media specific cluster however, but does include a headphone/mic jack .
Razer Blackwidow Chroma V2 - https://www.razerzone.com/gaming-keyboards-keypads/razer-blackwidow-chroma-v2 - Similar to the above two options, but Razer uses their own similar-to-CherryMX swiches (some would say "enhanced" others say "knock off" ). This version is the newest of their top level mechanical gaming keyboard, which does have USB passthrough and headphone/mic jack. It has macro keys but lacks the media cluster but like the Roccat puts the media functions as alternatives on the F keys. in the past I've had negative experiences with Razer hardware quality and software being overly intrusive with less functionality, but admittedly that would be a long time ago. Note that there are a lot of older versions of Razer Blackwidow keyboard out there so I'd only buy the "Chroma V2" for the newest and best experience .
Corsair K95 RGB Platinum - http://www.corsair.com/en-us/k95rgbplatinum - An excellent choice with Cherry MX "Speed" (Linear like "Red", but faster activation) or "Brown" options, this is Corsair's latest version of the K95 which has RGB per key backlighting (also notable is a decorative "lightstrip", which can be turned off if you like) as well as some additional mechanical macro-keys (plus media/volume cluster)! Corsair is notable for having beautiful brushed aluminum decks on their high end keyboards and this one comes in black or gunmetal. It also has the USB passthrough! Corsair's software has been improving as well and is now pretty useful, but like the logitech above once you save certain things you can stick them to the onboard memory and it works well even without lots of packaged nonsense. Don't want the macro keys? Then you want the K70 RGB RapidFire - http://www.corsair.com/en-us/k70-rgb-rapidfire-mechanical-gaming-keyboard-cherry-mx-speed-rgb-na - . There is also the K70 RBG Lux that comes in Red or Brown switches too. IMPORTANT: There are lots of older versions of these corsair keyboards that have different font, lack RBG backlighting etc... so I would only buy the indicated ones for the best experience (ie the single color K95 and K70 had problems with the keys going bad and backlighting going out that was fixed wit the RGB variety that mounted the connections differently).
Between them all I'd be most inclined to go with the Corsair, while giving them all a good look over. I have an early version of the K70 RGB without the USB passthrough, but it has held up well and the media cluster I find useful.
Note that there are also keyboards out there from other brands (ie Ducky Channel. I'd suggest the "Shine 6" or "One TKL RGB" ), but some of them can be tradeoffs or very expensive. If you'd like any more information please let me know.
Its hard to go wrong with many mechanicals currently. Find something with a layout that interests you and do a little research into current hardware features and QC (Geekhack and Deskthority are dedicated keyboard forums and will give you lots of info on nearly everything available). Even economy manufacturers (Keycool, Plum, Magicforce, Ect.) are worth looking at because mech-tech has become quite mainstream (I'd even rate a lot of these brands on-the-level or better than may popular "gaming" boards).
Don't focus on looking for something with feature rich software, since options like Auto Hotkey exist.I hate being forced to use manufacturer software for peripherals since it's often times buggy and gets little to no support beyond the first few months with new products.
Since there is not a lot of information on your post, I'll do my best to help. Here is an excellent article with information and A LOT of choices https://exposegaming.com/best-mechanical-keyboards/ . You can even click on the title to go into each article for more information.
I'd recommend the Razer BlackWidow Ultimate, I bought mine three years ago, and I still use it every day.
if you decide to go mechanical ideally you should try out a few different switch types.. some people really hate reds.. but I like them. no right or wrong answer just what people like..
and of course now there are many different companies making clone mx clones since the patents expired.. a lot of layout options as well.. I have settled on TKL as it seems to put less stress on my wrist with shorter distance between left hand and right hand on mouse..
and of course style question.. I see a bunch of "gamer" keyboards mentioned so far.. I can't stand the looks of most of that and I don't need or want a bunch of led lighting.. too each their own.. but RBG lit keyboards are not my deal at all..
ducky is a solid choice also.. however not an option for me as I personally can't stand cherry stabilizers.. but that is again subjective I greatly prefer costar stabs which is what the Filco's have as the OEM for them is costar.
I would recommend if you want to dip into the mechanical keyboard realm, get a switch tester or find a local meetup to try out some switches and boards. Once you know what you like, take a look at a Code, Ducky One, or even the Rosewill 9000. They are all well made boards that will last a lifetime. $100 is entry level for a decent mechanical keyboard. You can poke around massdrop.com for sales too and see what options there are to get started. The keyboard/mouse/monitor are the three things i physically interface with and therefore I'm a strong believer they are likely the most important to customize to your personal preference... and also if you invest in quality products they will last you a very very long time and through many builds.
Just to give you an idea, this is one of my more used boards.. an older Ducky that I use for 50 hours a week for many many years (mechanicalkeyboards.com has the replica of it thats exactly the same, different name). Note the 15 year old mouse thats still used daily as well.