You gonna overclock or no?
MSI is an overall good quality board with not so many confusing option in the BIOS...enough to OC if you really wanted to.
DFI are basically the current top best OC'ers you can get on the market as far as boards go, but even without OC'ing they are great boards....they have TONS of options in the BIOS though, but you really shouldn't need to go into the BIOS anyway honestly....even their non-SLI boards have two PCI-E slots though.
ABit is good, but recently they started to try and make their boards overclocking "user friendly" which user friendly and overclocking don't go together, either way though it's also a decent motherboard.
If you're OC'ing definitely DFI, if not I'd probably say MSI, then ABit.......other boards somewhat worth mentioning would probably be a Gigabyte board......personally I think ASUS is crap and you'd have a helluva time even trying to get tech support should you ever need it.
This is all socket 939 motherboards by the way, you definitely don't want to go with Socket 754 at this point.