I have to add that isolating my sub (DefTech SuperCubeI) made a significant difference in the overall sound. Tighter cleaner much much less boomy-ness. This is especially true for music.
I use Soundcare Superspikes threaded to replace the supplied feet http://www.taylorsales.com/SuperSpikes.htm

I actually use these same (but non-threaded) under my L/C/R speakers which areon built-in shelving and there again it is a noticeable tweak.

I recommend this fairly simple step whatever your chosen product. It just cleans up the sound so much.