it all depends on how much sustain you want on the bass notes if the bass is too heavy isolating it is a good idea but if it is too light coupling it is a better idea.
Subwoofer Footing - Connect or Isolate?
What is considered the best way to "foot" a subwoofer, should one try to connect it with the floor or isolate it? I have a REL 7i that I have firmly coupled to my wood floor with the weight of a 42 lb curling stone, mainly because it looks cool. Would some sort of isolation be better and reduce resonance from the floor, or could the connection with the floor help "drain" resonance from the subwoofer cabinet?