expat,
When i placed my M60s on a thick carpet w/o the spikes, one of them tilted left. The primary reason for using the spikes is set the speakers level on such odd surfaces, although by the time you reach the point where the speaker may be considered tilted to the point of 'off axis' it would most likely be falling over anyway.
The more surface area of the speaker that is in contact with the flloor, i would imagine there would be a greater transfer of bass into the floor surface as well. With a concrete basement, i haven't noticed any real sound difference though. This may change if i had wood flooring.
