After going through all this myself, shopping for speakers are so hard for this very reason. In addition, I often found myself comparing different speakers in different rooms, with different sound systems.
Shopping for subwoofers is even harder since they are even more dependent on placement and room characteristics. The same subwoofer would sound completely different in different stores. Some salespeople admitted to me that the subwoofer was probably not properly calibrated.
I am firmly convinced that there is no substitute for in-home listening of speakers / subwoofers.
