After some umming and ahhing, I've decided to stick to just iTunes. This means giving up a player I've used for ten years or thereabouts but iTunes has a trick Winamp doesn't*. ITunes's smart playlists mean I can use the 'comments' field like a tag. So last night I wrote "garage, lo fi, j-garage, covers" in the comments field for Long Tall Sally by The 5,6,7,8's, and the track was instantly added to a playlist of all tracks with "covers" in the comment field. Along with Marc Almond's Like A Prayer and The Delgados' Mr Blue Sky. Admittedly, that is a strange playlist but the key thing is that it is automatic: I add the comments and the playlists are built in the background. Web 2.0 functionality, oh yes.
*or, at least, I haven't found it yet.