Will this PSU power an HD2900Pro?

That PSU is a horrible choice, even though it technically can, I would go for better units. Remember it's also important the PSU quality and stability, it's pointless to have an unstable, but powerful enough unit.

My two suggestions:

Antec NeoHE 500 ATX12V 500W Power Supply 100Vac to 240Vac +/- 10% UL, CUL, TUV, CE, FCC, CCC, CB, C-tick - Retail

http://www.newegg.com/Product/Prod [...] eoHE%2b500

CORSAIR CMPSU-520HX ATX12V v2.2 and EPS12V 2.91 520W Power Supply 100 - 240 V UL, CUL, CE, CB, FCC Class B, TUV, CCC,

http://www.newegg.com/Product/Prod [...] ir%2b520HX

Both are high quality units manufactured by Seasonic, and BOTH output more current than the Rosewill that you chose. And the only feature that you cannot make use if you don't have an 8pin PCI-E connector is the overdrive feature, which allows for more power for overclocking the card even more.

I should have mentioned how tight my budget is.

$100 for a Power supply is a bit too much right now, but I suppose I could wait a little bit.

Oh, and the 2900 comes with a 4-pin Molex to 8 pin PCI-E connector, I should have asked if that would work just fine.

If anything, there was a nice OCZ PSU I liked for $90.
http://www.newegg.com/Product/Prod [...] 6817341010

Actually my budget is really tight, I can't fork out $90 for the OCZ either.

I don't want to wait for my next pay day either.

I see what your saying.

Maybe an 8800GTS 320mb uses significantly less power? Although, thats about $20 more anyway. >_>

For less than the cost of the first PSU you listed a Corsair VX 450W PSU $71 +$9 shipping plus $19 in rebates @ ClubIT. Corsair VX 450 $79 + $9 shipping and $10 rebate @ Newegg.
It will get the job done without a doubt.

The box says 550w power supply, but my 450 watt antec is doing the job just fine. I think those recommendations are just for people that have a crappy computer/cheapo power supply that doesn't actually put out the power it's rated at. Any halfway decent brand of power supply over 400-450 watts will get the job done. People buying 700+ watt supplies are wasting their money unless it's for crossfire and massive overclocking. Just look at the stats. Your card is drawing 160 watts even if you OC it to XT speeds. Then, your cpu maybe draws 100-110 watts if that's OC'd too. Now you have another 150 watts to throw around for all the smaller power consuming parts. Depends if you have a lot of Hard drives and a pci soundcard, etc... too. I only have 2 HD's and onboard sound, so the only other things that need powered are my mouse and keyboard.

Ok, I think I'm going to take the plunge and get an HD 2900 pro tomorrow. I have a 600W OCZ GamesExtreme PSU, which will be powering two SATA 7,000rpm drives, one DVD-RW drive, 2 gb of OCZ PC 2 6400 memory (once I get it back from RMA), and a e6750, which I want overclock to 3.0 ghz. Is the 600W enough? I'm a little worried since the specs say this card needs a 550W power supply, and the one I have is not much above that. However, there is a good chance that once the 2950s come out I may sell the 2900 I'll be getting in favor of the new hopefully less power hungry cards.