i guess u can mix brands of nvidias as long as the cards are identical, physically and virtually?

Yes, the drivers that were released during the 7000 series card allowed cross vendor sli.

Yep, as long as the chip is the same, it's good, I think you can have differntly clocked cards as well, but not sure the extent of that

yay

I'm not familiar with either Crossfire or SLI.

But after my experience with the Striker Extreme motherboard, which uses a Nvidia Chipset because (as far as i know) its required to make it capable of SLI use, i'd keep far, far away from both Nvidia and thier SLI.

With this in mind, i vote Crossfire.

Crossfire enabled chipsets are very hard to find, the Intel 965P chipset is one of the few I recall.

I've never had problems with SLI/nVidia, only had problems with ATI so far

Im with DarkLord, i used to have an ATI card and almost all my games would glitch up and/or not load, tried a replacement card, it still didnt work, after deciding that ATI didnt like something o else in my system i switched to Nvidia, worked perfectly 1st time, been using them ever since