Hard to say, depends on the rest of the system. Based on part prices, i5-760 is ~200 $, ATI HD 5770 is ~150 $, 4 GB RAM is ~60-100 $ or more. All parts are fine for a gaming system. You can spend even more for a faster CPU (i7), GPU (ATI HD 5870) and more RAM, but you won't probably need that ever.
"192 GB ought to be enough for anybody." (from the miniseries "Next Generation's Jokes")