Well, Ive done a little more digging. On MSI's site, they post a link to a review done by anandtech. They get pretty in depth with the review, and even run tests with 3 DIMMs (I assume they are using 3x 512MB). The text from the link is pretty much self explanitory
http://www.anandtech.com/mb/showdoc.aspx?i=2036&p=6
"Three DIMMs required 2-2-3-5 timings for stable operation, which is remarkably close to the most aggressive 2-2-2-5 timings available on the K8N Neo. You do need to be aware of one quirk in the MSI memory setup. If 3 DIMMs are installed with the memory speed set to AUTO, the board will down-clock the memory to DDR333 speed. To achieve DDR400 with 3 DIMMs, we had to move off Auto and specify DDR400 speed. However, DDR400 with 3 DIMMs worked very well in our tests, and was very stable, which is certainly a first for the Athlon 64."