By default I ended up with the Ultra SSs on the larger 3" stainless steel bases (can't remember what they're called). Jim Smith told me that the name of the game with my Duos is decoupling...not coupling them to my raised carpeted wooden floor. I decided to and did order the Grand Prix audio APEX footers but GP could not provide the specified thread pitch for the adapters so I went with the Stillpoints and pitched the brass spikes. The biggest inprovement for me was the large decrease in floor shake I experienced in going from massively coupled to the decoupled approach. Otherwise, there were marginal gains in low level detail , decay trails and intelligibilty.
Hope this helps.
Hope this helps.