I had a LaCie external SCSI CDRW drive from 1999-2001 and it never gave me a moment's trouble. I don't recall its specs. Every now and then the OS would lose the drive and I had to reboot to see it again, but I suspect that was more something with my SCSI card. I still have it around the house, but don't use it any more because newer drives beat it at speed.
I just got a Pyro Firewire case that converts any IDE/ATAPI drive to firewire. I'll be putting a Pioneer A03 DVD-RW drive in there and am looking forward to good speed and portability to my laptop (which would require a very expensive PC card SCSI adapter to go the SCSI route). You might want to consider that route if you're already going with an external drive. But if you go SCSI, you should definitely be happy with the low CPU utilization.