I just swapped out my old M5A88-M for a M5A99FX Pro R2.0 board. The '88 is going into a HTPC project. Anyway, I am extremely happy to say that I am easily getting the Phenom X4 965 stable at 4.3ghz with the NB clock at 2600mhz. The previous board would let me top out at 4.2 if I kept the NB right at 2000, or 4.0 if the NB was overclocked. However, I have a concern with the voltages that I am running. The "auto" option was pegging the CPU at 1.52v, and the NB at 1.35 at that speed. I dialed that back to 1.48 and 1.30 manually, but can't go any further without it crashing under any load. For the record, at just 3.8ghz, "auto" was 1.48 for the CPU, and stability was possible at 1.45 manually. Those numbers seem astronomical compared to where I read other people run the same processor with the same clock normally.
It may be that I am yet to get the feel for the more feature-rich BIOS I would confess. I haven't had the choice of multiple power-phase or load-line profiles before- nor many really advanced settings like "response speed" for the voltages.