Advice on which HU

I have narrowed it down between 2 kenwood units :

1. http://www.crutchfield.com/cgi-bin/S...i=113K DCX759

2. http://www.crutchfield.com/cgi-bin/S...o&i=11 3MP919


Waht are the real differences between these 2 units. I read everything crutchfield says but do not understnad some of it.

Will the 919 have better sound quality than the 759, or is the price increase simply due to mp3s?

Does anyone have either one of these or experience with kenwood. My former HU was a jvc till it was stolen. Thanks alot.