This discussion reminds me of the HBO show "The Rehearsal" where someone reproduces, with stunning detail, exact copies of various venues so that the client can practice a social interaction.
I don't see how ANY dealership now, or in the past, can come close to offering a similar set up to one's particular situation for an audition. Yes, many dealers will have sources that are much better, or worse, than your own, and it is simply unrealistic to expect a lot of choices for companion gear in an audition. Even if there were choices, how would you know which is the "correct" model for a meaningful comparison for your system? It makes sense to use the best possible source, to reduce its adverse impact on the sound, when auditioning other gear in the system.
You could try to arrange to either bring in your own gear, or arrange for a home trial. I know that some of the dealers in the DMV will allow either if they know you or have some confidence in you. But, don't expect an okay for a home audition of really large and difficult to move speakers or delicate turntables unless you and the dealer are REALLY friendly. My favorite dealers are Command Performance (Falls Church) and Deja Vu Audio (Tyson's Corner)--both are very friendly and helpful and you can probably arrange for a meaningful audition.