Isolation Advice Needed

Barry Diament, who did a number of pretty famous remasters, suggested a bicycle tire in an enclosure (if you want to get fancy); there are commercial variations on this, including obsolete stock from Townshend. You float the turntable on air. 

I have a problem in that the automatic -re-up (Vibraplane connected to an air compressor) might change the balance of the turntable. That is peculiar to my system, given the Airline arm (which needs to be aimed "downslope" to do its "thang"). :) Feel me? :)

I'd suggest a number of concrete piers to support the floor. If your builder can't or won't do it, you could add hydraulic jacks. Suspended floors bounce. 

Black Ravioli are made in Scotland and not well known in the USA.

Very well priced at approx US$260 for a set of four.

Will I get them back? Hope so. He also has one of my grounding boxes, and my Audience AU24Sx RCAs. 

Mechanical jacks under the floor are a cheap, stable option but will not solve the real problems of your stereo. You can effectively build a suspended floor under you speakers with the speakers mounted on springs and the suspended floor further mounted on springs and then the wooden floor.  Mine are blocks of laminated pine, built like mini butcher's blocks, 600mm x 450mm x 100mm. this arrangement isolates the speakers from the floor and the speakers from each other. Spring rates depend on the weight of the speakers for the first set of springs and the weight of the speakers and blocks combined for the second set of springs. Depression of each set should be around 25 - 35 %.  This is achieved by reducing or increasing the spring size and or number of springs. Nobsound springs are good but more expensive than others on Amazon. Total cost for my set up was approx $120.