Anything that spins, vibrates. Cat or no cat. Reduced vibration equals better sound.
For something inexpensive, try a bamboo cutting board (I like these), any of Herbie's Audio Labs footers (always a good deal), or the Vibrapods as mentioned. Even a foam mouse pad would work well. You could also try a cork floor tile, which would be another good material to dissipate energy.
For something inexpensive, try a bamboo cutting board (I like these), any of Herbie's Audio Labs footers (always a good deal), or the Vibrapods as mentioned. Even a foam mouse pad would work well. You could also try a cork floor tile, which would be another good material to dissipate energy.