Unless we're talking about turntable playback, the sound output from your speakers are not a likely source of vibration induced distortion in a hifi system. (I'm assuming reasonable sound levels and the avoidance of narrow band resonance excitations.) There simply isn't that much energy in the sound waves. A much more common problem is vibration transmitted from the speaker directly through the floor or walls. Rooms with wood floors in wood framed houses suffer this type of problem. I've placed my subwoofers on Vibrapods to isolate them from the floor. The total cost of this tweak was about $100 which is relatively cheap and a very small percentage of the value of my system.
What is vibration isolation for?
Where do these vibrations come from? From where I stand the earth doesn't shake too badly?! I would think that most vibrations would come via sound transmission through the air directly through the chassis of the components thus rendering the racks or other vibration isolation, uh, useless, no? (with the exception of actual thumping from walking etc)