I personally have the 7750 crossfired with my a10-6800k currently. Considering how cheap the 7750 is now, and how its only a few bucks more than the 6670 I would say its worth it. The resulting performance is about the same as a 7770 on its own. The micro-stutter is not noticeable in my experience, and it is certainly better performing than the a10-6800k or 7750 independently. After overclocking the a10-6800k's GPU and using ddr2133 ram (i cant get 2400 to POST oddly enough), the performance of the iGPU is almost on par with the 7750. The reason the 7750 works is because it does not require the crossfire bridge. Rumor has it the r7-260x does not require the crossfire bridge either because it supports PCIEx3 and XDMA. My socket FM2+ motherboard has PCIEx3 so i plan to pick up an r7-260x later today to see if it will crossfire.