For GPU rendering I use a GT 650 Ti Boost. Strangely, rendering jobs consume all my CPU time so anything else I do on the computer is just as choppy as when I do a CPU render.
I have Blender configured to use 6 of 8 cores when it does use the CPU but that doesn't help either. It's an FX8350 CPU, with 8 gig of RAM, so that should be lots of horsepower too.
Since there are guides for setting up multiple instances of Blender to handle GPU/CPU renders on alternate frames I would expect the CPU to remain largely free during a GPU-only render.
Does anyone have insight/tips as to why it's sucking up more resources than it probably should?