Tried memory between 900-1450, no big difference.
Running driver 13.8 since it also is a gaming rig and 13.8 is the best for Crossfire games.

Are the benchmarks made with N=6 or earlier?
Hashrate halves at each N-change.

EDIT: Giving up on solo mining, after an hour I got 2 coins and 2 rejects, need a pool.