Value-wise, 2133 is best for APU's, any speed under that has measurable performance loss, any speed over that has too little performance gain for the price. For an APU I'd also run 16Gb ram, since the APU is using system ram as vram, and the cpu is also trying to use system ram, so some games like bf4, watchdogs, MMO's etc that use heavy amounts of system ram don't tag the igpu as well, there is plenty to spare.