Keep in mind that good, cheap and reliable are contradictions in terms. You can pick one, perhaps two, but probably not all three.
That said, I've personally had troubles with both MSI boards and VIA chipsets. As a gaming machine the board you selected would be minimal in my view, but it might work out ok. I would look for something from ASUS, Gigabyte, or DFI instead, depending on the limit of your budget. I've heard Abit and Foxcon are also fairly good boards.
Yes, it does matter whether you use 667 or 800 ram. The 800 will give you higher overall speed, especially with a AMD cpu. Some Intel machines will do fine with 667, but they use different bus speeds and multipliers.