I'm not sure about the theory behind it... I've seen theoretical discussions where people have said that basic power equipment shouldn't affect gear with low current draw, but in my actual experience with some, it has affected the sound of every piece of gear, every time.
I've tried a handful of typical and ideal power strips (but admittedly no expensive strips or conditioners). For example, the Furman PL-Plus and the Tripp-Lite Isobar 6 Ultra. A fellow forum member took apart the Isobar and found high quality construction and parts inside, but we both found that it still influenced the sound quality. Whether it's better or worse will depend on your system, but regardless of the conditioning equipment I tested, the results were the same, especially with the amplifier plugged in: increased "blackness," sharp sibilance, boomy/flabby bass, narrower soundstage, and compression of dynamics. All bad things in my somewhat-resolving mid-fi system.
I moved to a non-surge strip for my source equipment and still plug my receiver straight into the wall. This leaves my gear unprotected from surges, but the sound quality is a great deal better, IMO.