Well...thread necro!
I just wanted to chime in about my L645 E6400...so far it looks like a decent overclocker. Haven't pushed it hard because I'm still using stock cooler and my P5N-E SLI has no cooling on the SB so that has me a bit
wary of frying something, which I've heard can happen on this board.
So I'm at 2.9GHz...nothing special, really. But what gives me hope and keeps me happy is that I'm at VCore 1.250

Memory is running unlinked at 1.89V @800MHz, with the NB at 1.295V.
Haven't had the time to run Orthos for more than 3 hours though...so I'll keep my fingers crossed and will leave it running all night tonight...the proof is in the pudding. I did have a very long Oblivion session and that went without issues.