Yes I realise as I wrote my first reply that what I am really interested in is a total id3 database driven solution to music management - both on the PC and on the music player itself. I will check out Media Monkey (particularly if it can be used to manage my current iPod). I have no problem with more complicated software than iTunes - it really does not handle large databases well in terms of speed, its many undesirable features and bad behaviour under windows, all annoy me more and more. At the same time I really don't want to revert to drag and drop methods of file transfer - choosing 60GB out of about 300GB is already complicated enough without opening and closing multiple folders etc, let alone deleting things again off the iPod. A simple syncing operation is very much easier.
The trouble with file/folder name navigation on a mp3 player is that it doesn't suit classical music very well, with often very long track names, and strange foreign characters that fool Windows all the time when you insert them into file names. ID3 tags care nothing about all of this, and make navigation much easier (or at the least more readable).
Also even with the iPods rudimentary virtual views, you still get more choices on how you access the music than a simple folder view. For example I can go about finding a particular album, or start looking for a particular artist or navigating through a genre I am in the mood for, depending on what I am trying to find. There is no easy way that folder navigation can replicate this multiplicity of views. So yes I am looking for a player that knows how to use id3 tags for navigation, and preferably with more flexibility than the iPod.
Thanks for the information so far!