it's free but with 'extras' ; depends on your definition of intrusive; what i hate is apps. that do stuff without asking like getting in your startup folder when you've told it no and things. like Realplayer and Quicktime etc.
Or you could try Jet Audio which plays QT, Real and just about anything else you can throw at it. I use an older version, there is a freeware version here:
http://www.cowon.com/eng/index.asp
It
also encodes to mp3 and has loads of other functions. Pretty good I say.