Did some research on the zCD and found out the disc drive is sourced by the same company that makes BD drives for Sony's Playstation systems. At low speeds its very quiet. The concept of the transport is for it to be totally enclosed, much like the DVP-S7700 I own, but not slot loaded. This kind of damping reduces noise a large amount, but makes servicing a moot point. If the drive has a failure it's typically more economical to just replace the drive. This kind of concept has been around since CDROM in the late 80s.
In addition to being small and quiet the zCD also has a huge host of features like the USB port and independent level control possibly negating the need of a preamplifier. The zCD also has an auxiliary input. If I had one I would connect it to my TV's audio output and get a power amplifier and that'd be it. Everything else on the rack would be sources.