Yeah the bios isn't super user friendly with old mobos. Since its not an unlocked processor you can't increase the multiplier so basically all you can do is increase the frontside bus and core voltage until it's stable.
Have you tried overclocking the q8200 because as far as i know the q8400 is just higher clocked. I've personally got a q8200 at 2.8ghz stable. It would be interesting to see the results then.
Well in that case, just look up headphone reviews and get the ones that have a sound signature that best suits your taste and then buy an antlion mod mic.
The sound is personal preference but these are good quality headphones, plus the removable mic allows you to wear them in public unlike the game zeros.