I have nearly the exact same setup. You can see what I have in my sig. 1 Phoenix under each Klipsch Icon Main. It is awesome I wouldn't have it any other way unless I could put my mains on the floor inside both of the subs. Honestly, the mains are great on top of the subs but it makes the tweeter a tad bit above ear level when sitting, so if I could put them on the floor inside next to the subs that would be why. Other than that I love it like that.
P.S. As far as the rubber between them. All I did was put the rubber feet on my mains instead of the spikes. It is totally fine.