Based on what you describe, I doubt the other speakers in the room had a significant impact. I mentioned it because it is a variable, however small.
I think you have hit on the major difference - acoustical treatment. I will tell you that this is a science unto itself, with many variables. Start with the walls in your room, compared to the listening room. Focus on the furniture and floor coverings as well. Move things around, and introduce new elements (pillows, rugs, chairs, etc) to the area.
You mention sound being different. Was the bass or treble different? The wavelengths of these are at opposite ends of the scale, and different materials alter them. Bass has long wave lengths, and large, thick items alter them...such as a sofa. Where as the wave length for treble is very short, and tapestry and curtains can alter them.
You can isolate your pieces using tiptoes, or other similar devices. For kicks I took a piece of MDF, about 5/8" - 3/4" thick and simply put 4 long screws through the corners. I placed my sources on it and noticed a difference in several qualities of the sound. Spikes on the speakers are recommended by some as well. CD Players and turntables are susceptable to vibrations, and all materials resonate at certain frequencies.
I suspect that the dealer had their room specifically and professionally treated to aid in their ability to demonstrate the products. You may benefit from speaking to them. Mass renovations may be difficult in your apartment, without finding yourself, and new stereo equipment out on the street!!!
Regards,
BBIBH
