Bring my own preamp to an amp demo?


I'm going tomorrow to demo a Bryston 4B3. I have a PrimaLuna Evo 300 preamp and Harbeth 30.2 XD speakers. The dealer suggested that I use a similarly priced preamp that he sells, but if I want to hear the amp with my specific preamp and the speakers I own (which he sells, and I bought from him) I need to drop it off when he opens and come back later because he has other appointments booked and needs time to connect my PL preamp, and maybe (I'm guessing) get it warmed up. I'm also going to listen to a BAT VK-56SE, and he suggested I keep an open mind and listen to an Einstein Integrated amp and thinking about selling my PL Evo 300 preamp. He wants me to have an open mind, and said he has a lot of customers that like and bought the Einstein with Harbeths. He also has an Audio Note amp demo for me to listen to as well. He's not a fan of PL, but is happy to work with me.
Bring my preamp or not?
128x128ctwith3
Bring your preamp, and your cables, and maybe even your source if possible and if the dealer doesn't carry it.

If you like it, insist on at least a weekend demo with the store demo amp (already broken in).  Offer to have the dealer put a hold on the funds on your credit card,  pretty standard procedure for this sort of thing.

You need to be able to hear it in your room if you're dropping that kind of money.
Agree with Vinylzone, if the dealer doesn't work with you walk and buy online with return rights. 
Bottom line, the fewer variables in your audition, the better.  If you can't audition it in your own home with your own preamp, speakers, and other peripherals in your own room, you're not going to be able to draw a reliable conclusion about how it sounds versus your existing amp. 

Bringing your preamp to his place will be better than listening to it with his gear, but it's still not enough info to make a solid decision about buying it. Not when we're in this price range, anyway. 
You should take the preamp home for a few days at least. No question. The real understanding of a piece of gear is listening the music after you stop listening to the gear. Then your subconscious forms an impression of the gestalt and you figure out if it moved your system forward or just made it different. .

My audio guy delivers and hooks the equipment up.