Hi Chris

Because the cabinet is a resonant design, what you stand it on can have a marked effect and to my mind is part of tuning the speakers to your room and system, allowing more or less cabinet contribution and also it's influence on the driver.

I find rubber feet OK under electronics but don't like them under cabinets. Try a board underneath, a granite chopping board is alright but wood sounds better, to isolate from either solid floor (put felt or something soft beneath) or carpet. You can experiment with the interface between them if you want a new hobby, but probably you'll find a nice result for damping and stability with simply a few blobs of Blu tac.