If you're concerned about which type of RAM would work well for you, then I'd recommend Crucial memory. Just go to their web site at Crucial.com, bring up your motherboard's manufacturer and model number and they'll list all the sticks of their memory that are guaranteed compatible with your motherboard.
The memory they sell is good quality. It's even got free shipping and a free lifetime warranty, so you know you're getting your money's worth. I'd recommend going there and checking out what they've got to offer.