Hey you think a Q6600 could reach those speeds with a boosted voltage? - Alex.
The Q6600 has a lower multiplier, so wouldn't be able to go quite as fast. Also, at the high voltage, electromigration starts to rear its ugly head. Even if temps are controlled, those electrons can start moving and suddenly you wonder why the computer stopped and why there's a slight smudge on the CPU.
That voltage, and the heat involved, is part of why the new expensive chips are nice. I can run 3890mhz (9x433) all day at 1.27v and 48c under Prime95, with 4050mhz (9x450) only raising the temp to 50c, still at 1.27v. That said, the speed reached by the OP is a good performance run, even though a tad warm.