I would personally get the 128GB drive and keep the 250GB platter drive for storage. Running RAID 0 doubles the chances of corruption and SSD failure so make sure you have a backup if you decide to run RAID.
While this is probably WAY more in depth than you need to go, I figure that I'd write up a small guide to calculate what would be best for your environment:
You mentioned that you are mirroring the 2 disks (RAID 1). RAID 1 has a heavy penalty when it comes to performance as you can only go...
I think that you just have bad luck with drives. Take this for what it's worth, but I work at the largest corporate storage array company in the world as a technician. I work with hard drives on a daily basis and can't count how many times that there is a hard drive failure on a storage array...
My vote is the 7970 as it would help you to future proof your rig. If you need more horsepower down the road, just buy another 7970.
I personally had the same decision to make when I was building my PC, but I'm glad I went with the 7970.
If you're going to spend $ on a new card, it would be worth it to spend a bit more to get a 670, otherwise, I would say to just buy another 570 and get a SSD with the money you would save from buying a 660ti. Just my two cents.
I found this case on Craigs list locally for $30! I couldn't pass up that deal so I built my rig around it. The case is a Falcon Northwest Icon 2 which is built off the Silverstone Raven chassis.
Another option could be to get a reference based 7970 that vents the GPU heat out of the case rather than into the case. The reference based coolers aren't the best for temps, but if you absolutely cannot get another case, I think a reference card would do better in this environment.
This is a bit drastic, but if you wanted to get the 4850 working and you've tried everything else above, you might want to try to re-paste the GPU with new thermal paste. I did this for my friends old card, and it lowered the idle temps by 15C. Anyway, just an idea....
Do you have access to another PC that you could try your 680 GPU in? If so, I would recommend that you install your GPU into another PC and run a similar test. If the card still artifacts, than you most likely have a faulty card and it would require RMA. Depending on where you bought the item...
I'd also throw a vote in for the 7950. Battlefield 3 runs amazingly on my 7970. It's true that crossfire will "stutter" and not play as smooth as SLI, but if you aren't concerned with that..... who cares.
If you are open to buying used items, you could even to bigger and snag a 7970 for...
If the OP would consider used items, you can snag a 670 for $300-350 on various sites / locally in the classifieds. I know that is more money, but well worth it if you are a gamer (future proofing).
If I were to pick one of the 2 options presented, I would go with number 2 due to the SSD.
The difference between the 460 and 7770 is minimal (460 1GB edition anyway). If you're going to buy a new graphics card, I would go for more power. A slightly more powerful option would be the AMD 6870 http://www.newegg.com/Product/Product.aspx?Item=N82E16814161389 This card fits the bill and...
I also went ahead and flashed the BIOS on my Reference 7970 (Diamond). All is well. No problems playing a number of games. I also enjoy the higher stock clocks as well as CCC having higher OC limits. 36,700 GPU only score in Vantage with stock clocks.