The memory is stored in the seat electronics (maybe the CCM but I don't think so), however the memory recall system is part of a greater good.
In a GLX which came with the power seats, the driver's seat, the car's mirrors, the intrument cluster, and the CCM are all tied together. Recalling a seat position also recalls the rearview mirror positions, and indicator chimes from the seat system are emitted from the instrument cluster speaker, which it likely gets the signals from the CCM. It is also the CCM which handles the mirror positions, so the link between the seat and CCM is most critical.
edit: in a B5.5 (cars equipped with the 1C0 CCM) the link is via the CAN-BUS. I do not know how the seat connects to the CCM in the B5s (cars with 1J0 CCMs). I'd imagine it's also CAN-BUS, which raises another big concern.
You need the power seat that matches your CCM. A new seat will not talk to an old CCM, and vice versa. You must also make sure that you use the correct harness for your seat/CCM combo.