I need to get an OS but will look for a sale on either 7 or 8 so don't include it in the budget unless it's a good price.
I have a Microcenter nearby, and honestly any online site with a better deal on parts than Microcenter would be fine.
AMD has the best offerings as far as budgets go, and I'm partial to supporting the underdog.
As far as OC'ing and SLI/XFIRE I'm fine with both.
My TV's resolution is 1280x768, Maybe I'll get a monitor at some point, but plasma TV's are great for gaming.
I was thinking an FX-8320 and 7850 but cheaper is always better. I'd also like some cheap but quiet cooling something suitable for mild OC'ing (both GPU and CPU). I need no mouse and no keyboard I'll have to string a CAT5 through the attic but I intend to use Ethernet. I'll be using HDMI for audio and video. I'd also like to be able to max most games on the market today and hopefully be able to play GTAV on nice settings.
Edit* Gah! I almost forgot the fact that the case size/color/lighting doesn't matter as long as it's priced well.