either setup is going to give you ridiculus performance, obviously the 470/480 also gives the added bonus of dx11 but it's probably going to run hotter then the 275's which will already run way hot as you probably already know
If you want a GT480 I would sit on it for a while. They only perform slightly better than a 5870 in most games and run $100-$150 more. I would assume they will continue to work on the GTX480 design and get a version out that actually has all 512 cores enabled and also maybe a lower power consumption model. They will probably call it the GTX485 or something like that. That is what I would l do.
If you are itching for performance get a 2nd GTX275 somewhere cheap, or dump the one you have and get a 5870. Don't even bother with a 3rd card for dedicated PhysX. Only a few games even use this and 2 cards in SLI will be MORE than enough. Otherwise the 3rd card will sit there and produce more heat and suck more power.
1) sit and wait for new GTX4xx model
2) get a second GTX275 (do not use a 3rd for physx)
3) dump GTX275 and get a 5870. This will give you DX11
Just finished building my PC.
Intel i7 930
EVGA x58 SLI LE
Patriot Viper Series DDR3 6GB (3 x 2GB) PC3-12800
Bfg GTX 275.
Should I go with 3x sli gtx 275 with gt9800 as a dedicated phyx card or gtx480/470 sli. I only play games in 1920x1200 regulation max.
If you only play at 1920x1200, why are you even considering an three-way SLI solution, when there are several GPUs on the market today that can handle almost anything thrown at them at that resolution? Are you just itching to spend more money than you need to?
Overclock the GTX 275 and be happy with it for now. That is what I would do. :-) it's free. It's still a good card. If you can sell it for a good price, I'd go for a 5870. The GTX480 is/will be at a premium price for a while.
In most case he's going to be correct, most high end cards from last generate could do that same for current games with a few exceptions of course, crysis (hate even mentioning it) the new metro 2033 in dx 11 which is suppose to be super demanding, and the new stalker i believe also in dx11
More than likely one 5870 will serve you needs, same goes with the 480gtx or an additional 275gtx in sli will bring performance past these options in dx 10