ok.. to all people who says motherboards will have no effect in gaming performance, you are all wrong lol
well... lets say it doesnt have a direct effect thats true, but its the mainboard which provides all the necessary voltages (via psu) and its memory lanes so the better quality will be resulted in a better performance as its directing better current to its loads (on an electricians point of view)
there is also recent a motherboard performance comparison here on Tom's you may want to look at.
and there the medal goes to ASUS (if i recall correct) by quality/performance point of view with slight boost over its rivals asrock/gigabyte/msi.
but as its told already, it will be a little difference probably you wont realize it without bechmarking...
or maybe you will. who knows lol
I'd definitely say go for asus/gigabyte they're the market leaders these days anyway... and lots of people are complaining about msi customer policy (if something happens to your board)
and asrock is the new kid in the block... eventhough its promising, I'd always go for its grandparents which has more experience in the field.