Time to change LINES

Personally, I'd keep 'em. Economically, they're already bought and paid for. Historically, it might be interesting to see other cars transit the new collection/layout. Realistically, you'd probably not be able to sell everything you'd want to and there is still the hassle of selling them or consignment. Grammatically, I'm out of reasons.
 
They're probably not worth as much to others are they are to you. I'm with Herc, you're better off keeping them. You could repaint them, or use them as visitors to your new location.

It might be worth it to attempt to trade off a few to get you started on the new line, but I wouldn't go so far as to liquidate the whole set. Personally I'd be upset to see all those memories rolling away.