Definitive 939 Motherboard Review
Tom's Hardware Guide Motherboards & RAM: Finally Available: Nine Socket 939 Athlon64 Motherboards! - Introduction. Yes, Tom's Hardware finally has gathered them all.
The main conclusion is that the AGP MSI Neo2 is one fast board. It is dual socket 939 and beats most of the newer nForce4 boards. For future proofing, it shows that the boards to drool over are the SLI ones, if you can afford them (at $250-300 each right now).
So, the net, if you need a computer right now, then the MSI Neo2 is the right way to go. If you can delay at all, then PCI Express won't be any faster, but upgrading to a new video board will be easier (of course, I've never in my life actually upgraded a video component, usually, the rest of the system gets obsolete too fast, but it is peace of mind.