As someone who has been building my own systems for about 10 years, I would highly recommend looking at manufacturer web sites to find the so-called "preferred" RAM/Motherboard/CPU combinations. Generally I start with the CPU and work out from there. I know AMD publishes lists of motherboards that they have tested and probably RAM as well, though I haven't looked in a long time.
In the past I've tried to save money by buying a motherboard that wasn't specifically listed on the AMD site as compatible, and had nothing but problems. That's not to say that will always happen, you just give yourself a better chance if you go with something that's already been tested.
says, it can be kind of a crapshoot. Electronics are sensitive and its entirely possible that, after all your research and hard work, you get a motherboard or other component that's dead right out of the box! (It's happened to me more than once.) The site you linked to has exceptional service in my opinion, and while getting a bad component is annoying at least you can get a replacement without too much hassle. Not trying to scare you, just prepare you for all possibilities
. Building your own system is rewarding and still has many advantages over buying one off the shelf, especially if you really want to learn more about computers. Have fun!