2 ATI 2900s 512 mb in crossfire better than one 8800 GTX?

Tough question dpending on the game, however, that said, if ATI's new drivers live up to what they are reported to do, it should be a lot better in a lot of things.

The 8800gtx is probably the smarter choice, but if you like ATI more, then 2900pro's are the way to go.

Ehhhh.... Probably

I had an 8800GTX, my water loop leaked and killed it.

I now have two x2900XT 512MB cards in crossfire on an x38 board (x16/x16 PCIe)

The x2900XTs are slightly faster but even in a case with massive airflow they cannot cool themselves very well, and the drivers are pathetically unstable.

I would give them away for a new 8800GTX tbh. Biggest waste of money ever.

SLI/CF Never scales 100%
Ie: If u get 60fps with one card u will prob only get 100fps with 2 cards.

Thats why it never makes sense going sli/cf UNLESS ur at the very peak of performance, like 2x8800 gtx. People wanting 2x7600's are just wasting their time.

As for 2x2900's. Given the massive price increase over a single gtx id HOPE they would be faster, but id still prefer 1 gtx.
I had a 1950xt (on water, which DID have a leak which i didnt see for ~24 hours till green fluid started leaking out the bottom of the case. Ran down from the cpu, down the mobo, pooled on the card, down the mobo, thru the pci slots. Didnt kill anything the )... and that ran quite hot, so i can believe 2x2900's being close to each other will run quite hot.

2x 2900pro's arent more expensive then a GTX, here in uk anyway, its £300 for a GTX and £160 for a 2900pro.

Idk if its different where I/you are or you were reffering to 2900xt rather then pro.

Old math.

2x160= 320
320 is > 300