The overclocked results for dx9 gaming are impressive, could you try FEAR or Oblivion?
Also what resolution(s) did you bench at?
I had been considering the 8600gt as a possible upgrade, I may have to reconsider now, the 2600xt appears competitive... I wish someone with a similar setup could run some identical benches with a 8600gt both stock and OCd.
Anyway nice work