Pardon another newbee question. Since speakers apparently have different impedences at different frequencies and various amplifiers' power outputs respond differently to different impedences, doesn't that mean that the actual frequency response of a speaker is very dependent on the amplifier?

Could this be an uncontrolled variable that accounts for the appearent variation in sound and reviews of different amplifiers; could the apparent sound variation of amplifiers be really depended on based on the speakers used in reviewing them? Is the output of tube amps any more or less impedence-dependent than IC amps?