Good SCSI cards are available from Adaptec and others. The Adaptecs are pretty widely used it seems. You can get an Ultra160 for a not so nice price of about US$230 if you just get the card (OEM box) and get it mail order. It might seem pricy but you will not be disappointed with the performance if you hang some speedy drives on it. Shop around and you might find a better price. If you have enough bays in your case, I'd go with multiple drives. (It'd be a shame to have the SCSI adapter sitting around waiting for a single drive to supply data. :-) ) I picked up a pair of 10K rpm 18GB drives for under US$90/each a few months ago. If that too much per spindle, 9GB drives were going for about $55.
Congrats on going totally Linux. I have several boxes that were built to run Linux as their primary OS but I
still leave a tiny bootable DOS partition out there for hardware tools like memtest86, BIOS flashing programs, etc. Either that or you need to get all those tools on a collection of floppies or onto bootable CD-ROMs.
Sounds like you're in for some fun.
Rick