I have just found this topic, and I would like to make a recommendation.
Xion (http://xion.r2.com.au/) is a low-resource media player from R2 studios. it is very simple to use, and can play just about ANY music file format straight out of the box. It is extremely customizable, with a vast range of addons and skins for every aspect, from the player itself right through to visualization engines.
(http://xion.r2.com.au/images/screenshot_front.jpg)
this is the default skin
(http://xion.r2.com.au/skins/monkeez/Onyx_full.jpg)
what I use, currently holds the 'most popular' position.