Serial ATA. It's a new hard drive connection technology. You can only have one drive per cable and the cables are much smaller. The intent is that it'll be faster than the old (parallel) ATA, but in practice, that doesn't seem to be the case yet. (Though it might now, I haven't really been paying attention for a few months.)

I know you said you like AMD, but Intel is making consumer-level motherboards now that are extremely competitive price- and feature-wise. I can't imagine anything more stable than an Intel processor on an Intel motherboard using an Intel chipset. You might want to check them out.