http://www.formfactors.org/developer%5Cspecs%5C4_Wire_PWM_Spec.pdf
It looks like you are looking for something that outputs a 25 kHz 5V square wave. It should be pretty easy to do with a microcontroller if you want to DIY.
Why Facebook? Email/phone seems more appropriate for a professional service.
Do you normally have customers buy photos through the smugmug printing service? If you do, then you need to update your prices. If you don't then you should turn it off.
What are your specialties? Where are you...
Speaker wire: http://www.amazon.com/AmazonBasics-16-Gauge-Speaker-Wire-Feet/dp/B006LW0W5Y/ref=sr_1_1?ie=UTF8&qid=1417678257&sr=8-1&keywords=speaker+wire
But most wire will work. Stranded copper is what you are looking for.
At that price, craigslist is your best bet. Otherwise there is this:
http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR5.TRC2.A0.H0.Xlepai+2020&_nkw=lepai+2020&_sacat=0
You will most likely need a 3.5mm to RCA adapter to connect to the amp and some speaker wire to...
What's your price range?
There are tons of thing like this on eBay, but I am unsure of the quality.
http://www.ebay.com/itm/TOPPING-TP41-TP-41-TA2024-T-Amp-2X25W-Head-AMP-NEW-/110630145949?pt=US_Home_Audio_Amplifiers_Preamps&hash=item19c2120f9d
Looking for some cheap DDR3 RAM. Pretty flexible on the size and I'll obviously pay more for higher capacity. Just let me know what you have. Looking for at least 2GB and 1.5v or less.
Thanks!
Next is a Samsung Galaxy Tab Pro 10.1 16GB WiFi (Refurbished). It is also in excellent condition and comes with box, USB cable, USB power brick, and Fintie case (LINK). SOLD
http://www.bensukys.com/photos/i-TTstMD5/0/XL/i-TTstMD5-XL.jpg...
You would want something with the same pixel density and a 1200p width. As far as I know there isn't really anything out there that would work well.
In your photo they are using 1600x1200 screens on the sides which works well with the 2560x1600 main screen.