I am happy to know that the floor support is more important. My floors are 3000 psi, 12" thick, 1/2" rebar reinforced poured concrete.
As to my system location, I have found that analog; in particular, is negatively impacted (as is anything) that I place between my speakers. I had to put my dual metal stands on one side wall, several feet in front of the left speaker. The stands are welded with a 50/50 shot/sand mix and when struck, sound dead (without the fill, they have a ring to them). The VPI VI is mounted on a 1 3/8" HDF platform resting on a Townsend Sink. Behind the stands are a pair of Acoustic Fields large 3" deep absorption panels, so nothing bounces off the cherry plywood walls. There are SR HFTs at the mid-point between the seat and speakers. I can’t do any better with this room but definitely, the side location works compared to the behind the speakers location.