FWIW, we didn't do a long remodel of ours, but we built a custom solution L wall, showing Stealth speakers (sub+sat), a picture roll TV, a mirror TV, and a wall for a larger TV with Cambridge Audio Minx micro-sat speakers.

In our meeting room we have a pair of in-ceiling speakers, a touchpanel that sits on the desk tethered by a CAT5 cable (PoE is lovely), and a TV in a popup cabinet. In that one room we can pretty much show all of our audio/video solutions without getting up from the meeting (the room has lighting control for lamps and potlights too). Then we have the "solution wall" to show a few other hidden technology concepts.

That really is just about as much as I think you have to show. I feel very strongly that you do not need a LARGE showroom to show a dizzying array of options. You will do much better by having a clean professional space for meetings, that allows you to demonstrate some basic concepts of what we do, along with some neat (high profit) aesthetic driven concepts. You have to sell to both sides of the equation. The first meeting we had in the new meeting room after reshuffling things, I had a popup cabinet sold into the job within 5 minutes. Then we started discussing other things. :)