Built my build...Underclocked GPU?

Your GPU is not underclocked. When it have 0 activity the GPU clock and memory clock goes down like your CPU to save energy.
At my 6950 when activity is 0 my GPU clock is 250Mhz and memory clock 150Mhz.

your cpu and gpu drop there speed,voltage, power usage when idle. this is normal and what u want. why run your stuff full pelt if there is not load on it another good side to this also is the stuff runs alot cooler means your fans dont have to work as hard therefore your system is quieter. you can change this within the bios for the cpu by disabling all the power saving features and for the gpu using catalyst control centre and the only time you would want to alter this is if you are doing serious overclocking and getting instability issues! so leave it alone its a good thing!