First of all, some advice from The Dumper: if you have a SWC DX2 get a DiskDual! Even though the HD can be a pain to set up, it sure is sweet once you get it working.
Any IDE CD-ROM will probably do. If it doesn't spin up fast enough you may get an error, then you just power off and on the DiskDual and retry and it works.
I believe that you should look for a drive with a cylinder limit jumper. See my post from awhile ago on this board about setting up a DiskDual with a HD. FYI, I loaded the files from my PC running Win 98 by plugging the IDE HD directly into my PC, then I moved the drive into the DiskDual. This is much faster than using the DD's parallel interface but it is more challenging.
http://users.cgiforme.com/mbruce/messages/4334.html
TD