Depends what you are willing to spend really.
Let me tell you -- I have 4 PS to my name thus far. The first one I had when I upgraded to my current e6600 with a eVGA 8800GTX on a eVGA 680i board was an older Antec NeoH 500 PS. I honestly thought it was not going to do the job for me considering I would also have 2 500GB WD drives and 36 Raptor, along with PCI Wireless card and a DVD-RW drive not to mention the high OC.
I used it for about a month (and OC'ing my system to 3600mhz with voltages of 1.56) and I had NO NO NO problems. This PS I spent I believe $75 a while back. It's modular and rocks. It?s well made and not sure if that line is still available but I would suggest that one or a comparable one from Seasonic like the S12 line.
However I could not leave things well enough along and a great deal came up on a OCZ GameXtream 700 Watt SLI PS and with rebates it was really good -- roughly $100 Canadian. I installed that and what a shock, it did nothing but make my system way louder. Still no better OC, I could not lower my Voltages etc.
I then got another great deal (which I do not regret) for a PC Power and Cooling 750 quad SLI PS. First of all I love the look but most importantly it's also DEAD quiet and it has the potential of running 4 cards (which I will never do) but if you do ever go SLI with 2 x 8800GTX you will need 4 connectors. You can still do this on other PS just that you would need adaptors etc and also this PS is certified to run 2 8800GTX cards and quad core systems. Anyhow again it did not improve my system performance wise but it's quiet and well made. This cost me $124 Canadian which was insane.
Again... the $75 unit did the job just as well as the others and in fact now is running my AMD X2-4800+ system with a crap load of stuff on it.
The OCZ I simply do not like as again at least I find it loud. I also have another Antec but this one is the TruePower 550 and again cost me about $70. I have not tried that one in my system bur rather my father has it in his AMD X2-3800+ system. That is also very quiet and well made.
I know for a fact all four of those PS have the correct power connections for the newer boards but the PC Power and Cooling has a whole bunch of extras to future proof it including a dongle off the PCI express connectors for what I assume the ATI X2900 video cards have. Anyhow something to consider.
One thing to add ? I did some research and found a few sites that explain how to properly test you power supply with a digital voltmeter while loading, idle and under full load. I did these tests to check the rails etc on the 3 of the PS I used on my e6600 system. Although I can honestly say the Antec 500 NeoH had the ?lowest? results, they were all rock steady and were all within the accepted limitations ? again proving you don?t need to spend a fortune on a 1000 Watt crazy-ass PS.