I have completely overhauled everything in my system with all new components except my 2 aging HD 4890s in crossfire.
What would be the best single gpu (not being the GTX Titan, GTX 690, or HD 7990), in terms of raw performance and cooling that I could upgrade to?
Money being no object.
Moreover, would it be a gpu that I could potentially configure with an identical second one for SLI or CF 3 or so years after getting the first one?
My current setup.
AMD FX-8350 CPU (Stock frequency)
Asus Crosshair V 990FX forumla-z MOBO
G. Skill 32 GB 2400mhz Trident X RAM (2133mhz at the moment)
(x2) AMD HD 4890 GPU (Reference cooled)
Asus Xonar DX sound card
Mushkin 120gb Chronos SSD (Boot drive)
1TB WD Velociraptor HDD (Games drive)
1TB WD Green HDD (Near line media drive)
Seasonic 1000w Platinum PSU
Phanteks PH-TC14PE-BK CPU heatsink
Corsair Link Cooling system
Corsair 800D Case (filled with AF 120 & 140 fans)
Dell Ultrasharp U2410 Monitor
Aside from the GTX Titan, the best single gpu cards currently available are the GTX 680 and the HD 7970. They trade positions depending on the game and resolution, so there isn't really a clear winner. Both can have a second one added, but 3 years from now, there could easily be a card cheaper than a second identical card that outperforms two of either of them.
I would go for the Sapphire HD 7970. I have three rigs with a Crossfire HD 7950 one with a Sapphire HD 7970 and one with a SLI GTX 670 and out all of them I find the Crossfire Sapphire HD 7970 the best.