I only tried Win-amp again for a short while after installing SP1, and then I uninstalled it. Too many problems.
Lots of other suggestions from other users here on the site.
Aimp is often mentioned;
I mainly use this for videos etc;
VideoLAN - VLC: Official site - Free multimedia solutions for all OS!
and I mainly use this for audio;
Spider Player - The Ultimate Music Player
I use other stuff as well, depends on what I want to do.