should I suspend a floor-standing turntable?

Stringreen, this certainly has not been my experience and neither is hanging from the ceiling. In one home I had earth below where the turntable was and used a three inch pipe with a screwable plate that really did help and in another house built on a slab putting the turntable on the floor was quite good. Elsewhere sheer mass was the answer. I once heard a system in Chicago where the guy got curbstones under his turntable. Each weighed about three hundred pounds.

Wall shelf worked great for me in Germany.
Germans don't use drywall .

Schubert, I can see where that would make a big difference. Where do they run piping and wiring? Or is it just plastering over the walling?

It varies, in apts electric is usually in half-moon pipe strips running up the wall painted same color as wall, you hardly notice them. Most rewire every 20 years.most sockets look like Hubbel grade .
Average German house has 2-3 foot space between outside and inside walls with cylindical terra-cotta round pipe between them.Walls are plaster over wood.
I live near one of the most up-scale suburbs in the twin cities and it amazes me that houses going for 750K use same
drywall as a 100k condo.