I wouldn't expect ideal results with this configuration. Electronic components like the AVR usually do best with a more compliant isolation like Tenderfoot isolation feet. On top of a subwoofer, the vibrational environment is much more severe than normal, though. Four Tenderfeet each placed on a Square Fat Dot would probably give you the thorough isolation and decoupling you need. You want the Tenderfeet in direct contact with the bottom of the component chassis--not under the stock feet. (Placing compliant material under stock rubber feet tends to unconstrain the rubber material, giving it more freedom to resonate and introduce sonic anomalies.)
Taming the subwoofer better with a dBNeutralizer-based product like Big Fat Dots or Gliders underneath, between the cabinet and floor, would be vastly beneficial as well. Brings out a better-defined and deeply linear bass, and should also make the decoupling interface between sub and AVR even more efficient.
With the AVR chassis, vibrations that you can feel may not necessarily indicate any sonic problem. It's what you hear that matters, not necessarily what you can feel. Much of the vibration that causes a lot of glare and grunge in electronic components like a receiver are micro higher-frequency acute vibrations that cannot be felt or readily detected.
With your present setup, you're likely to be sending "bad" vibrations from the AVR to the sub as well as the vice-versa. A combination of Tenderfeet and Square Fat Dots would very most likely remedy that to about the best degree possible.
Steve
Herbie's Audio Lab
