Hi Dave. MDF screwed to the floor sounds like a better option - less severe and easier on the eye than paving. As mentioned, I tried isolation pods under the speakers, but they were unstable. How do you get the feet to hold the speakers firmly? I have spikes on the top rail with the speakers sitting on them -this seems to work well, with blue tac underneath the stands. I agree that the Spendors need powerful amplification. I ran them for awhile with a Rotel RA-01 which gave a smooth, well balanced sound, but the 40 watts struggled at anything over moderate volume levels. I then tried a Yamaha AS-500. This had more punch but the sound was too bright and a little brittle. Finally settled on the Roksan K2 and I heard the potential of the speakers for the first time. I think it's a great match.
Linn Axis tt/Akito arm/Nagaoka MP200 or ATVM95/ML carts/Trichord Dino mk3 phono stage/dedicated PSU
Marantz CD6006/Cambridge 650T DAB
Tisbury Mini Passive II pre/Roksan K3 Dac/Roksan K2 integrated used as power amp
Atlas Element Integra Superior inter-connects
Spendor SP1s(1988)/Van-Damme UP-LCOFC HiFi 4mm cable