He's not a fan of PL, but is happy to work with me.
Bring my preamp or not?
I wouldn't expect a dealership to be a fan of a line they don't sell. Even leaving the economics aside, they may not have heard many of them.
At your level of audio system, you need to hear the 4B3 with the gear it'd be used with. No question about that. Whether that's at your own home or at the dealership first depends on the dealership's policies and your relationship with them.
Any sale should be contingent on extended home audition. If the dealer resists, remind them that Audio Advisor will give you 30 days to decide. Locals should be able to do as much for you as the mail-order guys, for heaven's sake.