I have a retail 600e, ca2 stepping, with msi-6309 mobo.
It's gameplay-stable at 866MHz at 1.65v and windows-stable at 900MHz at 1.7v.
There's really no way to predict how fast a particular cpu will stably operate. It's pretty much luck of the draw.
I would recommend the asus p3v4x because it seems to be simply a better-engineered mobo - and there a lot of users on this forum who can help you with problems.
I'm pleased with the msi-6309 for stability and easy overclocking, but I had to do a lot of tweaking to get decent memory bandwidth numbers.