Might as well be a be big and get a proper i7 *puts on flame suit*
IMO, when building medium-end systems like these, you want to find the sweet spot for highest value that's still very kickass. ie, i5 2500k + 570. Basically no practical performance difference than a i7 2600k + 580 setup while saving tons of money which can go to more RAM/HDD/monitor/etc.
Now if you actually want to build a high-end system. Then you're not even looking at a puny i7 2600K, you're either looking at the 980X or the equivalent Xeons with at least 2 580s in SLI. 'Cause my thing is if you really want to "go big or go home" then you might as well go big all the way.
Edited by nist7 - 1/26/11 at 12:51pm