Just providing a bit of input. I know I'm new (very) to this forum, but I have a few suggestions.
Firstly the 7950 vs. the 660Ti. To be perfectly frank, I don't notice stuttering in any game other than Skyrim (which is known for its direct preference of nVidia cards); I have a 7950. The 7950 is an excellent card for me, as I run Eyefinity (triple monitors). However, on a single monitor, you would not benefit from the VRAM advantage of the 7950, and you would be safer with the 660Ti (considering mainly that most games focus on nVidia support).
Secondly, Battlefield 3. It is well known that BF3 benefits from more cores, and so I have to disagree with PP Mguire's recommendation of the i3 3220 and instead recommend something like the 3570K (which I love) -- The 3570 (non-K) is fine if you aren't wishing to overclock. If you're tight on budget, I would still recommend the 3330 over the 3220 (0.2GHz bump from 3.0 with Turbo on the 3330).
If I repeat too much I apologise, but I didn't read everything in-depth and just sort of skimmed over:
- 3570K is great
- 1600MHz is fine
- 700W is a tiny bit overkill I find, 550-600W is probably better for your build unless you're planning on two graphics cards
- HDD is fine, though can I recommend an SSD? The difference is very noticeable with just a $100 investment in an additional SSD
- Since I just read you'll never xfire/sli, I would say 550-600W PSU is enough; spend the extra on an SSD (of course this is just a recommendation, since you have your mind set)
Now I'll go in-depth with graphics cards.
A lot of people say "The 660 is almost a 660Ti". More say "The 660Ti is pretty much a more bang-for-buck 670". Even more say "The 670 overclocks to 680 level and is therefore just as good".
With graphics cards, you get what you pay for. I would say the 670 is probably the best bang for buck in a card, and would recommend against the 660. I would also recommend against the 650--never get the 650, please.
The 660Ti is great and definitely worth the $80 in my opinion. But it is up to you.
1. If you don't plan to overclock, there's no reason to get the K-edition processor with an H77. They are cheaper and do fine for 1600. Don't be dismayed by the x4 PCIe slots; they aren't a biggie in my opinion and the performance difference between x4, x8, and x16 is much less than it implies.
2. Do you want lots of AA? If so, the 7850. If not, I would strongly recommend the 660Ti--great card.
3. Yes. The 660Ti is far superior bang-for-buck.
I do hope someone actually reads this wall of text, but again meh.