http://www.crutchfield.com/S-zvcG2RV...0&I=500CDA9830
vs
http://www.crutchfield.com/S-DLnMnId...0&I=500CDA9851
there will be subs and components hooked up to it
i do use a lot of mp3s both are mp3 compatable the 9851 says something about being very fit for mp3 play.
the 9851 has 2v outputs as compared to the 9830s 4v output
i just can't decide
there's only like a $10 price difference