Vibration Problem

Adding weight on top can sometimes help as well as below.

Try 5 lbs of sand in a large ZIP-LOC bag on top of the player, (smoothed out flat over the player, not lumped in the middle).

Use the cones also under if you have them...

If it works, you can put the bag in cloth or something, if you care about the look...

How do you hear vibrations of your CD-player?

I had great luck with Bright Star Air Mass 3 which can be had for about $100 new. The cheap equivalent is to sit your player on an innertube with just enough air to float the player, too much air raises the resonant frequency and reduces effectiveness. This solution works great for heavy footsteps, deep bass notes, etc. which can cause some players to mistrack momentarily. Mine just sounds smoother at loud volumes too. You could probably try the innertube on the cheap and go for the attractive implementation if you so desired.

See tweaks at http://www.audiotweaks.com/