I'd go for the AMD too. But I would first start with what's causing mysql to take up so much CPU usage. And yes, SCSI drives are alot better than IDE drives, mainly because most SCSI controllers are superiour to IDE controllers.
ok thanks guys the AMD it is. I will also gt the SCSI then.
I know what is using the CPU usage. The forum part of the site is coded badly and uses over 2000 queries to return the forums when a user is logged in. It is searching for every new post since the user last visited. Except it searchs through the entire database each time!