I went to the Asus site to look at memory compatibility but it doesn't list much for 4G(2x2G) memory. Specifically Gskill. Does the memory have to be specific to what is recommended from each manufacturer or is all DDR3 ok? Also the specs for the board say 1333 O.C. I read somewhere that is not correct for 1333. I will be using an Athlon 640 along with a XFX HD-577A-ZNFC Radeon HD 5770 (Juniper XT) and will not be trying to overclock initially. Should I stick with 1066? I have spent some time researching all of the components I will need but the memory thing is a little confusing right now.
Most DDR3 modules will work on that board, the memory compatibility is just a list of memory modules which are guaranteed to work. The motherboard says 1333 MHz (O.C) which means you'll need to overclock to run the memory at that speed, by default it will run at 1066 MHz but in all honesty there's not much of a difference. Just buy whatever's cheaper, and try to buy memory with lower latency if possible.