Why are you getting an 8800GTX?
Get an 8800GT or an 8800GTS 512MB and save some money. The G92 8800GTS even outperforms the 8800GTX in many benchmarks, and costs less.
As for you PSU question, get something better.
This one is a great unit, and costs $70 after MIR:http://www.newegg.com/Product/Product.aspx?Item=N82E16817139003
It's 450W, but has 33A on a single 12V rail, which is probably the highest amperage you'll find on a sub-500W unit.EDIT
: Hehe, DellUser beat me to it. The link he posted has a better price, so go with that.