Need Advice on Amp Audition at a Dealers

buy a spl meter to ensure level matching, otherwise you will most likely prefer the louder setup....
have fun !

Verify with the dealer that they are OK with that. They might not be to protect their assets in case something is wrong with the amp. 

If they are local an in home demo would be best as always. 

I think bringing a "comedy stunt" amp that sparks and smokes a little would be hilarious.

Agree you must ask first about bringing any of your own gear!It would be good if they already have your speaker type and model as demo units, but not a deal breaker. And if they say no you just have to understand it IS a big deal. (what if something breaks. Who pays? YOU?)
Best thing is to bring music you know really really well. Make sure they know you are bringing music to listen to.(Sometimes dealers only stream...)
(for wolf_garcia.. At this point you are suddenly banned from 34,294 Audio salons in 26 countries. And you wonder... Why???)