Sandstorm3000 :
DragonBorn1511 :
theonerm2 :
It looks like the cards in quad sli would probably have enough horsepower to match a GTX 670 but the low vram would hold it back in newer games. So it would probably perform like a 750 ti 1GB in new games but under ideal conditions it could perform like a GTX 670.
not really worth it by the time I have a SLI Mobo and 850W PSU
If you already have those cards, you could do it. I am still running a single GTX285. Which runs all the games i want to play medium - high settings with 60fps. (Far cry 3, Need for speed most wanted 2012, LoL, WoW) And the low VRAM shouldn't be that big of a deal since a lot of the newest games are DX11 only. So you can't play them anyway. But for DX10 games you should be able to max out a lot of them at 60fps.
I've found a few GTX 295's, £40 each second hand, an 850W PSU will cost £40 over a 550W, then I'm spending an extra £35 on a SLI Motherboard, compared to something like a 270X + a 550W PSU, that's so much more expensive for no performance gains.
I think I'll stick to 1 GTX 295 just for older DX10 games, I play my AAA games on PS4 anyway.