I got a AMD Phenom II X6 1090t at 3.8GHz (OCed). Will that be enough to handle a GTX 670 single AND SLI? Other specs are:
1.5TB HDD Western Digital
16GB G.Skill Ripjaws RAM
850W Corsair gold plus PSU
ASUS Crosshair V motherboard
EVGA Nvidia GTX 550TI Fermi 2GB each SLI setup
You should be fine, but why not stick with the 550ti for now? It may not be a very powerful setup compared to the 670, but it should run virtually any game you need it to. Maybe wait for the next generation of cards?