I guess you have plan to use dual-graphics cards in your mind.
It's also my tough choice between Gigabyte GA-X38-DQ6 and Abit IX38 QuadGT.
IMHO, based-on my experience with Gigabyte GA-8KNXP,
I prefer Gigabyte hi-end products.
Its website is much easier to use than Abit
You can now try to download BIOS files and manual of each brand
and see how difficult and clumsy Abit provide to you.
Plus Gigabyte takes good care of their hi-end products
(often BIOS release, good manual, loads of accessories, nice components on board)
FYI, I don't hate Abit at all.
Every products has pro and con of its own.