Variable speed playback: Slowing down playback of music without affecting pitch

[StringTheory]

I've been looking for an MP3 player that will support variable speed playback of music.  I heard that Rockbox supports this, so I may have been looking at the problem backwards.  Perhaps I need to find a generic player that fits most basic functionality, and is well supported by Rockbox.

Any recommendations?  I'd prefer relatively good sound quality, in that my main interest is music, not audiobooks.  I'm a musician, interested in slowing down fast sax and guitar solos).  And it would be great if the player had capability for adding more memory (MicroSD etc).

I've owned a couple Samsung YP-P3 players, and they worked well for this.  But the touch screens -always- go bad on those.  (If anyone knows where to find replacement screens for YP-P3's, that would also be great, but I've pretty much given up on that).