Components on floor

Do you mean that the hardwood is directly attached to the concrete (ie: glued?)  My components sit on the concrete slab under my house, si the result should be similar. A 10,000# slab is pretty stable so there's no problems with vibration, though I  understand that surface waves can travel on top of the concrete but that's obsessive, even by my standards. Wire dressing is no more of an issues than with a stand. Bending down at my age IS an issue. The preamp and streamer are both remote equipped but the turntable is a pain! I've considered a sand filled concrete pylon to put the table at chest height but have not yet done so. Dust needs vacuuming daily. A unexpectedly significant improvement comes from not having anything sound reflective behind and between the speakers, which is where my components sit. It's like gaining an extra foot of wall to speaker distance. Overall, I love it!

You should be fine.  I have a floating wood floor and I have a lot of issues with vibration.  We have an extra bedroom in the basement with a cement floor and there’s absolutely no issues.  

I have mine on finished plywood which sit on short legs. Each component sits on anti-vibration pads. Only issue is the dog likes to lean on the plywood!

No issues. I had amps on the floor. Much better sound than having it all in a rack. Spread the components out and you’ll be fine. If they are at least 1 foot away from the fireplace you’re good. However if they are on the same circuit as the fireplace you might get some AC line noise. See how it all sounds. 
 

I have all source components on a DIY decoupling shelf system. I have suspended floors. My subs sit on Stillpoints SS, my monos sit on a Symposium Ultra each with HRS footers. This does a great job. I agree that a spring setup under wood platform would be A very effective solution.