LL21, I know from personal experience the Ultra 5's have great synergy under Vitus products, and there is no doubt the U5's would kill the factory feet, however I have reservations about installing them sloped side down. U5's sound best sloped side up imho. And Stillpoints were obviously listening as new stock U5's now have threading on both the bottom and top of the foot (as denoted by a blue dot on the side of the box). As usual, thread adaptors can be ordered to suit various applications. This is a better solution all-round as it allows the U5's to be installed in the superior sloped side up orientation, whilst the larger diameter thread should make the thread adaptor stronger. I know of one other audiophile who installed U5's sloped side down under his Magico speakers & bent a couple of the thread adaptors 'walking' his speakers into place, so that is another positive. It also permits the option of installing the Ultra bases, adding height adjustment whilst further improving the U5's performance.
In summary, yes definitely the best feet under what is one of the best ss stereo amps in world, though if it were me, I would not pre-install the feet, but rather supply a set of 4 U5's in the box with thread adaptors to screw them in (ssu) if desired. That said, I would personally install them with the optional Ultra Bases straight under the chassis & experiment till I found the best location.
