You know, I never really tried the iGPU on mine. I would assume so, I believe they just call it HD Graphics, runs at the same clock speed.
Here is firestrike iGPU results vs HD 4600, graphics score is just under half what the 4670 HD4600 does.
Wow, you are brave with that board.
I have a PCMate board / G3258 combo as well, I didn't push mine that high, I stopped at 4.2Ghz just because I don't really need faster than that (its sole purpose is to use one thread quickly to drive my NV GPU while doing OpenCL tasks). Good to know I could probably shoot for a bit higher if I feel the need later.