The new C Class has a 6DVD changer, and a 4gb HDD, so that's upto 55gb of storage/MP3's/Movies (I assumed the DVD changer can play Dual Layer disks in my calculation).
I don't know whether it's software or hardware (!) that won't allow MP3's to be played in the MLS via DVD's, but it is a bit of a flaw.
I too wouldn't buy a Merc in the current climate. They need a whole generation of cars that are like they bused to be. They've started improving again, but it'll take a while yet before people get teh confidence back. I think that new C Class is very well made, but the whole experience needs to improve and time will tell.
unfortunately the c-class 6dvd changer isnt standard. its only optional extra.