Ive just tested mine with a +135 on GPU and +750 on the memory, all seems to work well- though in the game i tested (MWO) only the memory boost seemed to have made a difference by about 10 fps(from 49 to 58~ for example)
PS> though the temps on the CPU became 82C for a short time, and averaging 76-78C - that might be because of other reasons but im just pointing it out in case its because of the GPU boost