Instead of using a SCSI CDROM can't you add USB to your A1200 and use an external USB DVD? That's what I'm doing on my A4K, on the DENEB it's also a lot faster than any of the alternatives.
This is an A1200 he has. I doubt a Subway gives more speed than the SCSI-kit since Subway is 1.1 speed only. Deneb is another matter since it is faster. SCSI all the way. One can get an SCSI-IDE adapter to use IDE drives on SCSI-chain.