Best and Worst presentation

Regardless of the equipment that was being auditioned

What was the best acoustically treated dealer/homeowner showroom?

What was the worst?
Their equipment is first rate. Their staff is friendly and knowledgeable. Their showroom has the acoustics of an old barn. (Or at least it did the last time I was in there 4 years ago.) I referring to Audio Concepts on Preston Road in Dallas, TX.

The thing about that, though, is that any gear I bought from them always sounded much better, AFTER I got it home. :)

As for the best, I'm still waiting to hear...
There could be a bunch of gear in one room but SPEAKERS you have to audition without any speakers standing next to. If the dealer hooks them up to you next to other -- ask to remove. The next standing speakers' drivers will definitely create extra resonance.
Stereo Exchange, they put in a new audio room several (maybe 6 years ago). Very expensive and "well engineered". It was the worst. As it turned out, the bass traps (which were actually resonators built into the wall) were all tuned at the same frequency (100Hz I believe). So the result was no response at 100Hz and uncontrolled responses everywhere else. Best room: Stereo Exchange, after they figured out the problem and fixed the resonators to the variety of frequencies they originally intended. As it turns out the room was well designed, and well engineered, but apparently someone thought if they built all those "things" (the resonators) the same, no one would notice--oops. Now the room sounds great, and it is truly a pleasure to listen to the equipment--and not the room.
Best: A shop in El Paso, Tx. of all places. The setup was Infinity IRS Ones, AR D-79 amp and SP10 preamp. I don't remember the analog system but it was sweet, sweet, sweet.
Worst: A shop in Phoenix, Az called Sounds Like Music, I seriously don't believe these guys have ever heard live music. Good gear but horrible sound.