Mechanical/Electrical transducers are the problem.
1. The microphones used to make the recording.
2. If you play an LP, the pickup.
3. The speakers.
IMHO These account for about 95% of the sound quality, assuming that the electronics are at least midfi stuff (Denon, Rotel, Adcom, NAD..etc.) Getting that last 5% costs all the money, and is a complete waste of time if the original recording wasn't top drawer.
PS: Really good or really bad room accoustics can play a big part even if the overall quality isn't great. I have mentioned before how good dixieland jazz sounds when played through honky horn speakers in an unfinished cellar.
Some professional performance halls have accoustic panels that can be raised and lowered so as to alter the hall accoustics to suit the particular performance format.