Making My Own Computer

[NoodleKnight]

Instead of only considering on what you want the computer to do, you should also design your computer around your budget limit.
And, from my experiences, Dual-Channel DDR does make a difference, but not that much, best save your money for something else. I've always stuck to intel processors since they generally are a bit more reliable, and run less hot, than AMD's. AMD's are much faster and cheaper, though.

[gobeavs]

Dual channel RAM makes a difference in Intel setups (and some with the regular Athlons), but not as much with Athlon 64's. The Athlon 64's on-die memory controller makes the RAM so accessible, that another channel to access it from doesn't help that much. There is so much latency with the RAM in Intel setups, that dual channel memory helps.

As noodlenight said, the budget issue is paramount. If you are tight, then that barebones system you picked out seems to be an excellent choice.