Philips make a lot of DSPs - this one is mask programmed. It's a much better bet than a general purpose DSP as it has specific car audio features - plus internal ADCs, DACs, etc. It's much cheaper than a general-purpose DSP, and smaller - a general purpose DSP plus 4 DACs, 4 ADCs, software for FM stereo decoding and RDS extraction, program/data memory, etc, would simply be too large.

A general purpose architecture would mean a much more expensive product that probably wouldn't fit into the box, and would require lots more software effort on our part.

Hugo