Ok, i need an upgrade from my single GTX 275, I could care less about power needed as I have a 1000w PSU. My GTX 275 says it HAS DirectX 11.0 (I don't know why, It says this in NVidia Control Panel). Which would outperform the other? If the ATI 5870 is better, can I still use Nvidia PhysX in games? And lastly, can I use the ATI 5870 and GTX 275 simultaneously to support more moniters? Also, should i wait for the Fermi to upgrade? My RES: 1920x1080
agree with the majority here. Your GTX275 will serve you well for little bit more. And Fermi's release being around the corner, I would definitely wait if you want to upgrade. Also know that GTX200 series are obsolete and discontinued. I do not recommend buying another GTX275 to SLI, the money you will spend vs. performance gain won't be worth it. I am in a similar situation as yours. I had GTX285 and was waiting for the card's price to drop so that I could SLI the card. Instead of the price going down, they completely discontinued the GTX200 series and they are even more expensive than how much I bought the GPU for. (i spent $350 about a half a year back and now they are $380-90). So I ended up selling my card for $320 and am waiting for Fermi's release so that the price of 5870 will drop. I would not have done this if I was sticking with 1080p resolution but recently, Ive been looking into 30'' monitors and i would want a decent graphics card that will be able to drive the monitor with most of the FPS games.
So yes, my advice would be...(in order)
1. your res is only at 1080p, don't upgrade yet
2. if anything, wait for fermi's release (to see price drops)
3. don't SLI, sell your GTX275 and get HD5850/70