Iterestingly there is Songbird which is developed of mozilla code base .IPod support other than on windows is a little broken.
A desktop App should use a plugin based architecture. Running basic app with bare minimum features should be cheap. If user wants to throw in the kitchen sink then his system deserves to be trashed. Coming to think of most of the apps developed today with the latest tools turn out heavy even if the app has nothing great to offer. And thats why VC 6.0 is still sweet, hell even GTK is lighter. Check out Reaper with all the works still comparatively light. Reaper screenshots : coolio.