CknSaladI would try to get the Nvidia 660 TI or AMD 7950 for $300. Cpu I would opt for the i5 3570k.
Case is honestly subjective: bitfenix prodigy, sg08, or lian li q08 (mitx), lian li a04, sg09, tj08-e (matx), fractal arc mini (m-atx). Personally if you are only going to have one card and maybe a dedicated audio card with just a few hard drives, I would just opt for matx as mid towers are pretty damn big.
Ram I would go with g-skill as they have been in the business for a long time. 8 gigs at 1600mhz is enough and should be around the $50-65 mark.
Motherboard: I would pay for at least a $130 motherboard (make sure its the 1155 socket if you go with ivy bridge, i5 3570k). Gigabyte and Asus are my favorites probably by far to go with. Asrock I hear is a hit or miss as their quality control can be inconsistent. MSI is a decent cheaper alternative.
Hard Drive: Mechanical drive I would go with Western digital blacks as they are very fast. A good thing to try is a Western Digital Raptor 10000rpm drive with an SSD (Get a Samsung 840).
PSU: This is easy, if you're going with a single gpu setup, honestly a quality 450-550 watt psu is all that's needed as pc components have gotten much more power efficient over the years. Brands to go with are: Pc power & cooling, corsair, seasonic, antec, enermax, rosewill capstone line, kingwin platinum series. I personally would go with gold modular as you get the best of both worlds: good power efficiency and using only the cables you need, which means less clutter and easier cable management inside the case.
Hope this helps!
For psu go with a quality brand like seasonic. For hdd just get segate. You can get a 1tb 7200.14 for $70, or a wd black for like $100. Both work fine.
About the gpu, the 660 ti is a terrible value. I own one and use it in my build, but only because I got it on sale for $230. At the current price ~$300, its not worth it. I'd just go with a 7950 and overclock it. Even stock speeds it beats the 660 ti on most games. (not trying to be amd vs nvidia, its just a fact that the 7950 outperforms it).
3570k - $230
660 ti - $300
vs
8350 - $160 (ish)
7950 - $260-300
The 3570k is $100 more than the amd fx cpus, or even more if you get a combo deal with motherboards. You can find a fx 6300 + 990 fx ud3 mobo for less than the price for the 3570k alone at micro center.
Here's a comparison of the 8350 vs the 3570k. On a lot of games, the 8350 beats out even the $300 i7 3770k
http://www.youtube.com/watch?v=4et7kDGSRfc