Len,
Break into the 21st century man!!
Ditch the 6 disc. If you don't have an iPod at least go to an a headunit with MP3 compatibility.
It would open up your shopping list massively.
I am probably biased - I'm really not keen on Sony in-car stuff. Don't get me wrong, Sony make some great products, but IMO they're all home-based - PS1, PS2, PS3, PSP, anything with a Bravia badge on it and pretty much their entire camcorder range. But, in-car? Never been a fan TBH.
Spend some money, get an ipod and an Alpine deck with an iPod dock, or at the very least an MP3 compatible CD deck.