What source do you use to demo equipment?

It is astounding that the very dealers who decried the quality of digital sound now routinely stream (in digital) when demonstrating downstream components, even when these rival luxury cars in price.

The benefits for the dealer are obvious - they can likely find whatever the prospect wants to hear in a minute or so.

Ask if they can play SACDs and you get blank looks - "oh, I think we've got a player somewhere".  Even then, it will likely just be two-channel and a royal pain to set up.

My audition pieces include Benjamin Britten's own performance of A Young Person's Guide to the Orchestra originally recorded in analogue by Decca around 1963. This contains almost every instrument of the orchestra except the piano, and covers individual instruments playing soft and loud, building to a crescendo with the full orchestra playing to multiple cross rhythms.  All in 18 minutes.

I do not have the analogue record, but similar sounds are on Sir Adrian Boult's recording of Elgar's orchestration of Bach, as noted by AI. 

The record of Sir Adrian Boult's transcription of Elgar's orchestral arrangement of Bach's Fantasia & Fugue in C minor is a well-regarded recording with multiple releases. It was originally released by EMI in 1974 with the London Philharmonic Orchestra, and later reissued on LP by Mobile Fidelity Sound Lab (MFSL 2-501) and on CD by EMI/HMV (CDM 7 63133 2) in 1989. The 1974 recording was noted for its excellent sound quality and the performance has been praised by critics. 

I also have Hyperion's recording of Shostakovich's Piano Concertos on both SACD (no longer available) and record.  The second movement of the second concerto brings out the air around quiet piano notes, especially on SACD.  Of course, streaming does not generally support multi-channel DSD, as far as I know

I buy and try new equipment with my home system whenever possible.  I listen to Who’s Next on CD and a Best Sounding Songs playlist I created on Qobuz.  At dealers I stream on Qobuz.  

@richardbrand  “…It is astounding that the very dealers who decried the quality of digital sound now routinely stream (in digital) when demonstrating downstream components, even when these rival luxury cars in price.”

True. But in all fairness the advances in streaming in the last ten years has been at break neck speeds in comparison to typical evolution or revolutions in high end audio.

I take my old but still good FiiO X5ii Digital Audio Player (DAP) and it's coax cable to connect to the DAC being used by the showroom.  The DAP has two larger MicroSD cards which are loaded with my favorite lossless CD rips or lossless audio downloads..

Good old fashion vinyl does it for me, except for reissues or fully digital new albums. After multiple tests with different system, vinyl natural and organic sound is  very difficult to reproduce all things being equal. That being said, high res streaming has come a long way over the past few years.