Yes its true, and also of course, the newer of motherboard you get, the newer archetecture your going to get.
For example, you could get a motherboard that supports new RAM, as most models of motherboard at the moment support a max of speed PC3200 RAM, though RAM goes alot faster than this in the market.
Also newer motherboards can support newer processors features, like for AMD it would be Cool n Quiet which needs compability of both, and also Dual Channel support which would also increase performance.
A motherboard would increase overclocking potential yes, as this is what carries all the data too and throw. It also helps that they allow for good components to support the overclocking too.
So yes, its best to go for a make you know is going to do well.
I mean, you could seriously got for great components, and get a cheap motherboard and it'd work, yet, you wouldn't get the full potential of what your computer has to offer.
I'm afraid I don't really have any suggestions, but of course, its going to be a PCI-E motherboard, correct?
This would support the latest video cards, and probably would have to be to support CrossFire anyway. Though I don't know of any that are out at the moment I'm afraid.