To answer your question, I'll give a brief explination of what I use. My setup consists of 4 hd's (1 scsi, 2 sata's & 1 ext. usb).
The scsi hd is hosted by an adaptec scsi card (which both are needed if you plan on using other peripherals with it).
The only drawback is that it's a little slower (at data transfers) than the newer technological hd's, but is still reliable never-the-less.
I doubt that just installing a scsi card will yield all the results you're probably after, but storing and loading midi file data and audio samples via scsi hd...no problem.
Read more about this here
SAS and you should get a brighter picture of what you might decide to go with.