I tried bumping up Vcore a few times, ending up at 1.2v actual (1.2325 I think in Bios) and ran Prime for an hour each time to gauge if they were in sync or not. It seemed different cores would be falling behind every time, and the problem was not really consistent, worse some times than others. The system seems rock solid in all other aspects of computing, games, audio production (particularly CPU intensive), etc.
At this voltage, I decided to play around a bit, and took the machine up to 450fsb, resulting in 3.8Ghz and see if I could get a failure out of Prime95. I ran it overnight, about 11 hours and 20 minutes, no failure, but the cores were off by a spread of about 4 tests still. So it seems no matter what I do to it, it's Prime stable but not in sync.
Should I keep going with the Vcore bumps? The temps hit 60C on the hottest cores on RealTemp last night so I think if I have to keep bumping voltage, I'll have to start bringing down the clock to keep things somewhat cool. Or since it seems stable in everything else I should just let it fly?
Thanks again for all your help