thanks guys. I think I am just going to give the 660 sli setup a shot, if I don't like it I always have 30 days to send them back for a refund minus a restocking fee.
Quickly looking at some single gpu benchmarks of the GTX 660 and the 7950 at stock clocks performance is roughly the same,So according to that an sli setup should give you much better performance than a single 7950 the only thing you will be losing is 1gb of vram.Since you can send the cards back within 30 days i would definitely give them a shot,just go ahead and don't think about it,i know i would if can return the product back after purchase for a refund.
SLI doesn't mean twice power (sadly) 660 despite good, is lower than 660TI that is more or less like a 7870 so NO it won't be better than 7950 (and i am clearly not an ATI fan), so exept having better driver with NVidia , switching to a 660 SLI is a step back in performance. a second 7950 (even second hand) seem a nicer solution if you need extra performance
I just looked up one of Hilberts review of a gtx 660 and the graphs show at 1920x1200 the 7950 performing very close to a 660 just take a look for yourself for example Battlefield 3 average fps for the gtx 660 is 42fps and the 7950 40fps. I agree to this much better than spending cash for 2 new gpu's
I have a 660ti SLI setup overclocked at 1100Mhz and can say yes it can beat a 7950. It'l even beat a 7970 and 680 easily. It will also give a titan a good run for its money. I use it in tri monitor 5760x1200. The only game it has trouble with is bf3 when you put it ultra everything with (HBAO) 4xAA. It does fine on 2xAA and plus i like to have the settings turned down a tiny bit due to too much clutter when looking for enemies. Ive only seen bf3 use upto 1.75GB of VRAM.