I agree with Richard about that.
PCM1, whilst it's nice in that it provides readout for mpg, etc. and a telephone (which can be useful, albeit only occasionally), the map provides little more than a pretty decoration. The tape unit doesn't have any of the usual refinements (e.g. rewind) and, besides, I guess that it's only very rarely that anybody plays tapes nowadays. The CD is good in that it takes six discs (preloaded in the luggage compartment), but I guess that it won't be long before docking for iPods, or similar, is pretty much standard, so shortly to be superceded (i.e. already being superceded). Fitting an aftermarket system is the way to go so it shouldn't be much of an issue buying a car without the Porsche system installed. There are several on here with experience of choosing and fitting an aftermarket unit so help is at hand.
Personally I'd be keen to go for litronic headlights, sunroof, heated seats (not vital but a nice touch), and probably a PSE (but you can add this yourself).
The mileage is encouraging (not too low to indicate insufficient use and not too high to suggest it's been worked hard).
Overall, condition and mileage are the deciders.