I would start with the subs.
At first sight that might seem odd advice because it's known that our ears are far less sensitive to bass distortion than any found in the midrange.
On the other hand in real world terms if you are likely to have audible distortion then it's more likely to be found in the low bass than anywhere else. This is due to the greater movement and work being asked of the drivers and the cabinet.
You should definitely experiment with isolation because going from a concrete to a wooden floor is a fairly dramatic switch in support.
Equipment placed on wooden floors seems to benefit far more from some form of isolation too.
A simple method might be to initially use some cheap foam/rubber under each speaker.
Perhaps some experiment with placement too if your situation allows. I recently watched this video which shed some further light on the complex issue of boundary reflections.
Perhaps it might be of some help to you.