If you can go for the new 125W 9950, with a quick look through some Phenom databases, it's been getting much better overclocking performances than the 9850, especially since you'll have an SB750 board.
Too much on a 9600GT IMO, you can get yourself a 9800GT
for that money. The 1GB of VRAM has minimal performance benefits.
Since you're going with a 790FX/SB750 and some quality RAM, I take it you're overclocking. You don't want to skimp on a cheap PSU if that's the case. The PSU is the most important piece of hardware in your system and it's supplying power to all of your components. It needs to be able to deliver quality stable voltages. Even if you have to spend a little more, it's worth it. OCZ 500W
<- Amazing price after MIR.