GT440 is the "problem"

grab a 460/560 or a 5770/5850 and you can achieve what you want...

Your processor is fine

BTW 2600k can't be a bottleneck

ATM I have a @4700 mhz 2600k becouse on this PC i usually try benchmark and other..but with stock 2600 k i don't have problem of bottlenecking (on a 590) or on other setup