I think it'd be helpful to split this into two cases:
Regarding 'helping' the sound by steadying electronic components, it'll not help one bit. Solid state amps aren't effected by vibrations, and as for the CD-player... digital is digital is digital. Unless it's skipping due to some thumping bass, it's fine.
Regarding helping sound due to equipment vibrating and making rattling noise because of it, pads might help. You can do it cheap like 2x did. To see if you need to worry about this second type of vibration, just run the sub and turn the volume on a bass-heavy track up. If you don't hear any weird rattles, you're golden.
