well here try this,look up on google "motherboards compatible with ati radeon x1900xtx" or type in ATI Radeon x1900xtx compatible motherboards. you should get some lists of what you can get and maybe some user reviews on the motherboard then start looking aruund in stores or on ebay
instead of the Gigabyte, get this one: http://www.newegg.com/Product/Product.asp?Item=N82E16813131589
the extra 20 bucks or so is definately worth it. Its a more stable and more overclockable board than the Gigabyte. Nothing beats ASUS when it comes to reliable and fast Intel boards.