the speaker is the last link in your system between you and the music. you are seperated(or connected) only by soundwaves moving through air. IMO speakers introduce the most distortion into the sound, and this must be pleasant to the owners ears. IMO speakers have the most room interaction, this can lead to problems that can't be fixed. IMO speakers vary in sound to a higher degree than amps, sources, preamps, or cabling and each of us have their own preferences. IMO speakers can cause more issues with fit in the room and WAF than other components( if you move to a new house the speakers have a high chance of not working, higher than other components). so my conclusion is that speakers will always be traded more frequently. well constructed speakers that are well taken care of can last a long time. these can be an exceptional buy on the used market. units like processors and digital players, which become obsolete quickly, seem to command higher resale, this has always puzzeled me.