Best way to keep REL sub from “hopping around” at high volumes

I like the sound of springs over sorbothane.  I  think Herbie's is platinum infused rubber.  Many choices once you get this solved you will love the bass.

Honestly, I have to question subs playing that loud. I found that when they were set more than very low in my audio system, they collapse the soundstage and screw up the midrange and treble. They should not be heard.

I used to have 4 800 series subs, two in our HT and two in my audio system. When properly adjusted one could barely feel vibration from them with heavy bass. In my home theater playing the depth charge scenes from U-571 shook our whole house and they would vibrate a little with one’s hand on top.

From what you say, there is something very wrong.

+1 for the Auralex Isolation Pads.  Have the Auralex Isolation Pads under both of my JL Audio subs, on a hardwood floor, and I have no issues at all with vibration with the subs or the floor.  And I listen at high volumes.  Highly recommended.

Nice and simple. The same thing happen in my room as well. Just use Blu tack. If you are getting vibrations through the suspended floor cut a square slightly bigger then the foot print of the sub using 3/4 birch plywood (stain it) and put some blu tack in the corners and middle, stick the plywood to your wooden floor then place the sub on the plywood with the blu tack on the legs of the sub. All your problems will be fixed.

I have 2 SVS sb3000. There is no jumping around.  Look at my system.  I agree with @ghdprentice , something is wrong.