Gskill is a good brand and it has good prices.
Here you have the list of compatible memory modules.http://www.gskill.com/configurator2.php?pid=2&search2=bTRhNzh0LWU=&model=372
I would suggest you to choose the cheaper ones.
If you can't get Gskill, then look for Team or Kingston. Corsair is the best but they are very expensive.