According to the french fanzine Quasar CPC, the CPC Max! is an hardware expansion for the CPC, featuring an eZ80@50MHz, 512kB of video ram, a Mélodie card-based sound expansion, an IDE controller, a bi-directional parallel port and a serial RS232, and USB. This card will work with the original OS, but will also be compatible with ANA.
The CPCMax! will also have various already existing extensions onboard: ramcard, memcard, and maybe some others. It will be pluggable on a CPC or available as a stand-alone version.
All these informations are old, there are no new messages on the CPCMax! mailing list since 2003 and the project seems to have changed a lot since that.