the cpu wont bottleneck the gpu in terms of graphics performace, BUT you will see a hit on cpu intensive games/ applications (such as rts games, or any game with heavy ai - b/c the cpu has to do alot of 'thinking') because its a budget cpu.
I guess you're gaming. You want a quad-core. The new games use all four cores. A CPU can bottleneck a GPU, but not as easily as you might think. It doesn't take much CPU to serve a card. But the game itself often wants more CPU than the Athlon you mention.