I prefer Clementine, Amarok, and Rhythmbox. No point using a proprietary app when there's plenty of open-source apps which are just as good if not better...
As someone who adores Clementine, using it all the time, and as someone who has contributed patches (both bug and feature) to it, it isn't lean. My instance right now (running for over a week straight, playing music most of the time, I have around a dozen playlists open, and I have it auto download a half dozen podcasts) has 122M of resident memory usage, and 85 minutes of execution time on an i7 at 4.5ghz.
A really lean music player wouldn't use more than a dozen MB of resident memory (after whatever libraries need loaded, but since i run KDE Clementine isn't bearing the blunt of Qt loading) but Clementine intentionally caches a lot of information to make the UI lag less and make transitions seamless.
