apu, 8120, 6100 will bottleneck the 680 at varying degrees. they bottleneck a 7970 which is slower than 680 typically.http://www.tomshardware.com/reviews/gaming-fx-pentium-apu-benchmark,3120-10.html
if you want to get a cpu which won't bottleneck a 680, an intel core i5 2500k/2550k or i5 3570k or higher would be the best bet.
from amd, may be phenom ii x4 980 or x6 1100t. but sandy bridge and ivy bridge cpus will perform better still.
this month's $2000 sbm build uses a gtx 680 with an i7 3770k -http://www.tomshardware.com/reviews/core-i7-3770k-overclock-geforce-gtx-680,3212.html