I would recommend the 8MB cache, as you will find general disk performance increase, especially in heavy disk usage situations (such as booting, copying large files, or most games.) Obviously if those things don't really matter that much to you, then a 2MB cache would be fine.
You will only be able to use SATA on a motherboard that supports SATA (Serial ATA). Only newer models support it. It has substantial performance and features than the standard ATA133/ATA100 that most motherboards use.
Brands? My personal preference is Maxtor. I own a number of their 8MB cache drives (including the 80GB model). I haven't had any problems with any of my (maxtor) drives, and they aren't noisy when accessing data on the drive. Other people swear by Western Digital.
- rp
Edit: I guess iNeb and phrozen_dreamz beat me to it..