Just noticed this post...got a couple of thoughts.
The PSU is going to be the most inportant part of the system. DON'T get a cheap one. It will only cost you more money in the long run when it dies and takes out you MB, or vid crd when it does.
Right now for best quality across the whole range it's almost impossible to beat the CORSAIR PSU's. If you want modular, then the 620HX will power your system nicely. They have the 1000HX coming out soon, but that would be total overkill. For non-modular they have the 650TX and 750TX. While it 620HX is only rated at 620w, it's rated at 620 continious at 50C, and that's equivilent to other mfgs 700W+ whm rated at 25C which is what most of them do. At any rate, the 620HX, 650TX, or 750TX will all work for you. It would mostly depend on how much mony you want to spend. Check out this page
http://www.jonnyguru.com/index.php for PSU reviews. He's about the best there is for PSU information.
One thing you didn't mention was a CASE. Since you are looking at an 8800, you have to remember that those rascals are LONG. If you have the 'average' mid-tower, it's going to be a tight fit. I can HIGHLY recommend the Cooler Master CM690. It's a 'largish' mid-tower, but has plenty of room to put in the new LONG vid cards, but still dosen't take a huge amount of desk/floor area. Plus it's VERY easy to work with when installing your new 'goodies'. I was using the Cooler Master Centurian 5 which is a nice case, but my x1950 jusr barely fit in it. I upgraded to the CM690, and now have lots of clearance from the card to the HDD's.
Here's a good review of the CM690:
http://www.cluboverclocker.com/reviews/ ... /index.asp
And, a nice pic of one with very nice cable management. Note how much room there is from the 8800 to the HDDs here:
http://img.photobucket.com/albums/v154/ ... 010282.jpg
The CM690 has one more advantage. It's quite reasonably priced.
Hope this helps you a bit.