Well I have had the Pandafeet (blue) under my XR45 for a few weeks now and I haven't wanted to take them out. The Pandafeet are placed evenly under the four corners of my XR45 and I have a bag of lead shot on top of my amp to load them properly (I will switch to sand when I have the time; the lead shot was just here on hand so I used it).
I think the differences were subtle under the amp but positive. If you have ever used Sorbothane style footers under your Source or speakers you will be familiar with the benefits of this great material.
PROS:-Even more silence between quiet passages. (blacker background which surprised me as the Panny is already a champ in that area)
-Midrange feels a wee bit more relaxed & open.
-Bass is still tight and firm which is a product of the amp itself but the footers did nothing to hurt the bass which is a good thing.
-Highs were just a touch smoother (very slight but noticeable)
-With a 30 Day Money Back guarantee...it's a no brainer to just try these out.
CONS:-Sorbothane can ruin the finish on wood surfaces and other things as well. If you want to avoid this, just put small pieces of wax paper on both ends of the footers.
-People who own heavy amps (generally tube amps are quite heavy) will have to purchase two sets because they only support a certain amount of weight.
-They don't magically take themselves out of the package and jump under my equipment.
So for $20 and a $2.00 bag of sand for proper loading, I have found a good way to isolate the digital circuits in my XR45 and make subtle improvement on an already excellent budget amp.
I would highly recommend this product to anyone looking to isolate their amps, DAC and/or transports/CDP's. Folks with sensitive tube gear could really benefit from these feet .
PSI tried these footers under my transport and everything I mentioned above was even more true and apparent (seems transport mechanisms are more suceptible to vibrational engery...big shock there I know 
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