Sorry, couldn't keep my sarcasmn in check, welcome to anandtech forums
No hardcore gaming equals no dx10 card, even the high-end cards have trouble playing dx10 games at acceptable settings, and the highend cards start at 260$+. I've been repeating this for at least a week now, and I'll repeat it again. Buy the 150$ x1950xt 256 mb from saphire at newegg.com, it's a pretty powerfull card, a lot of bang for your buck, and I'm betting it will run even the new games in dx9 at decent settings. Crossfiring isn't an option, unless you crossfire two 2900xt's, for low-midend cards it's not worth it, coz most of the time your better of buying a single, more powerfull card.
The 8800gts 320mb for 260$ isn't a really bad option though, I've got one myself, but I only got it because my 7600gs sucked ass, and because I figured having a dx10 card for lost planet, call of juarez and crysis etc would be a nice thing, the 100$ I spend over a dx9 card like the x1950xt is well spend imo, since it simply is faster, and is dx10 like I mentioned. If I didn't game as much as I do and review games like I do, I probably would not have bought it.
PSU depends on what else you have hooked up in that PC, with a x1950xt, I'd go for a 400w enermax liberty, or perhaps a 500w liberty if you think you're gonna upgrade to a new videocard sometime later. Theres somewhat cheaper options, yet still decent though, like fsp/fortron for example.
As for cooling, whatever CPU you're gonna run on it, the stock cooler that comes with it should be good enough. Something better, might keep the chip cooler, and is adviced when oc-ing. It can also help in making the system less noisy, but if neither is important then the stock cooler will be fine.