Vibration is a killer of high sound quality. Subwoofers are vibration devices. So if you want good sound quality, no. You want very sturdy, heavy (typically filled with steel shot) speaker stands to place the tweeters at the exact listening level. Isolation devices improve sound from already solid footing. As also pointed out you want to optimize both speaker placement and subwoofer placement and there is nearly no chance those will be in the same location.
Bookshelf Speakers Sitting On Dual Subs?
I have a couple excellent subs - Elac Adante 3070 - which have pretty effective DSP. I'm thinking of buying the Dutch&Dutch 8c (also DSP). The Elacs are rock solid. I'm thinking about placing the 8c on IsoAcoustic stands on top of the Elacs so the 8c is even with the front of the Elacs and separated by the Iso stands: running the DSP for the subs and then the 8c. Any real drawbacks to this set-up?