XmPlay is free, uses minimal computer resources, and will even play music from inside rar/zip archives.
(Which is great, because I store my albums in rar archives along with their cover art.)
Free plugins expand the program's capabilities and there are lots of amazing skins and visuals.
I purchased Winamp many years ago and used it until it became a resource hog and borderline bloat-ware.
I have purchased several apps (Winamp, etc.) but I totally love (and exclusively use) a free program that will play anything due to it's plugins - XmPlay
Best of all - it is not a resource hog and is completely configurable to suit your own taste.
One thought about rar files to interject:
Rar files have the ability to have recovery records incorporated in the archive(s).
I create all rar archives to have 10% recovery records so that they cannot get damaged while transporting them (Whether the transport is from pc or web, the recovery record in WinRAR validates the archive.)