mpc007 :
However I'm not that sure your CPU is bottlenecking now. One of my setups has a Pentium G860 tied to a HD7850 and there are in fact not much games which have CPU usage at 100 percent.
If you run a game that's heavily dependent on single-threaded performance and runs the bulk of its code in a single thread, you can run into CPU bottlenecks on a quad-core/thread CPU even while Task Manager is reporting only 25% CPU load. With most games running a "busy wait" in their main thread, one core is always stuck at 100% usage on whatever core it is running regardless of what is happening, which makes it that much more difficult to determine whether the thread is bottlenecking on the CPU or something else.
The simplest bottleneck test is to either lower or increase game resolution with vsync off and see if that makes any difference. If the CPU is the main bottleneck, performance will remain almost exactly the same. If the GPU is the main bottleneck, performance will be strongly correlated to pixel count on the screen.