Also Feather linux has good graphical tools
off the top of my head any pentium will do this fine
486 is a bit light on the power to play mp3's but feather has worked on these too
On my P1 233 laptop all these will work fine
and both feather and Puppy can be remastered if required to make a customised version for your own use. All the howto's are on the puppylinux website
I'm building something:
I need a linux os that is on the skinny side but has support for GUI and Audio.
I need a very simple linux audio player
and a need pointed in the direction of one of those sites where you can get your cd track info - ideals a place with an API
AT the moment this 'thing' is purely proof of concept.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic