I actually went trough a "floor upgrade" with the same sub about a year ago. I went from carpet to hardwood floor (real hardwood). To date I cant say I have noticed any substantial difference with the subs performance. I have to be honest ... I was hoping it would be dramatic - but no. If anything - it seemed to add a lot of echo that creates a whole new problem to deal with on the upper frequencies.
I'm running the Sig S4's so I need all the bass I can get. I thought the sub would be a huge performance increase but I cant get it to match up right for my taste. Im kind of a bass junkie but I think my destiny lies on a different path. I'll keep the Seismic for movies it's a brute. I dont think you can go wrong with it if you can get it to match up with your speakers.
I wouldnt listen to us however - go to a gravestone shop or a shop that puts in counter tops ... see if they have some reject marble or better yet granite. I bought a 1" thick piece once for a different project for $15 it was 24" square but a little marred up. Give it a try - what the heck. Bricks, cinderblock, concrete squares ... it's cheap and worth a test.