Tom, thanks.
You mentioned the SVS water heater that they had there and that it looked shorter than you had imagined. That sure looks like a 25-31 PC-Plus, which has the shortest body style. The other models (20-39, 16-46, Ultra) are all taller. The second number is pretty much (but not exactly) the height in inches. So, the 20-39 would be almost as tall as the tower speakers, and the 16-46 and Ultra would be taller than the towers. They all have the same diameter.