Tried 2406 BIOS. No new BIOS options, however this BIOS for me is really bad, as I couldn't overclock at all. Anything I tried for manual settings didn't work and machine wouldn't boot.

I'm now back on 2403 and running at 3.0Ghz on a E6600 with CPU Vcore = 1.325v, mem = 2.1v and memory running with 4-4-4-12 timings.