Im not a fan of Asus, Haven't owned one since 939. From what I have seen and heard from others, it seems there is not a great upside or downside to them. BTW their site is ass...
Gigabyte on the otherhand has been great, big heatsinks on most of their offerings, great reviews. Outstanding tweeking options.
I just put some peices together for Defect. It's not really cut and dry what to get, but If you go AMD check out this board!
http://www.newegg.com/Product/Product.a ... 6813128443Its a good start anyway. It has USB3 works with the X6 out of the box
A couple of things to think about, it seems the newer mobos have 8pin power connectors. If you haven't updated the PSU in a while you may want to evaluate it and decide if its time for a new one or get an 8pin adapter.
Also think about weather you want a fast chip out of the box or are you willing to OC? Then you have to think about a cooling upgrade.
To sum it up look for motherboards that tout lots of options for OCing i.e. voltage and FSB tweeking (assuming you hang on to this for a few years and decide to eek every last bit of power you can out of it.
Keep your eye out on memory, Certainly not gonna be your bottleneck at stock speeds anyway, but the tighter timings can be a clue as to the quality of the chips themselves.
Processor, Highest clocked dual cores are the kings of gaming(for now) with the hex-cores and a market FULL of quad cores It's only a matter of time before games take advantage of all that power.
Video card...I am not the guy to ask, I have a gts250...It plays everything on high or better. But apperently it's junk.
There are tons of options. I would say choose the MOBO that suits you and your upgrade path.