I have a hopefully easy question...I look at the ram spec for the GA-X48-DS4 on newegg, and it says DDR2 1200, but in their RAM finder I can't find a RAM suggestion for this model mobo. According to Gigabyte I get several options, none bigger than 1Gig, as listed here.
The QVL is the ultimate guide for this boards ram, having said that you should be able to buy ram from a quality manufacturer and have it work just fine.
Personally I think DDR2 1200 is over kill.Now depending on how much ram you wish to buy and what OS you will be running I would look at ram that is a bit less expensive.
32 bit OS get 4GB
64 bit OS get 8GB
I would pick something out of this group.
http://preview.tinyurl.com/667drn But if you wish to get faster ram this group would be good to pick from.
http://preview.tinyurl.com/5pb7ke I like GSkill and Mushkin