CSMK2 was designed with A4000D in mind, so it's best compatible with it, as if you ever wish to attach the optional SCSI module, the fitting is most user friendly with A4000D systems as the included external connector SCSI backplate was made to fit with A4000D case in mind.
A3000, A3000T, and A4000T are all also compatible, however fitting and using the CyberSCSI module with those is a little more user-unfriendly, due to the specific design of the SCSI external connector plate.