I can't understand it (although, the Acards that I just bought "new" looked used). It works fine with either cable and either ATTO card with the Quantum drive. Even if I plug in the Quantum with one of the new Acard the Quantum continues to work fine while the Acards give errors. It will not boot into multiuser mode or even finish its boot with the new Acards. So, I am really unsure why I am having problems.
Two things: one, connect them to an OS 9 machine and make sure the firmware is the latest (download the latest from acard.com.tw). Two, try using a separate SCSI terminator at the end of the chain.
I know the older Acard firmware had issues negotiating SCSI bus speeds. John