Yeah, since that is a high end card there will be bottlenecking.
However, if you overclock it to 4.5 Ghz or 4.8 Ghz, the bottleneck will greatly diminish.
Unfortunately, there isn't really a good cpu upgrade from yours, yours is pretty much the top of the line cpu for your motherboard.
Only option is to get a new mobo, and in that case go to Intel, intel has better gaming processors as well as future cpu support.