When I first installed my SCSI drive I got seq read 44MB/s, seq write 16MB/s while my IDE drive performed 35/35. I read somewhere in this huge forum thread about converting to NTFS and dynamic disks. After
doing that I got read 46 and write 45 MB/s which I am happy with for the time being (measured with Sandra Prof benchmark).
I have not had time to follow the whole thread so I might repeat what others have said. but I still want to share my experience with you.