Footers under big heavy speakers (Stillpoints Ultra 5, Sistrum rack, Finite Elements,..?)

My new Super Stiff Springs are intended for *very heavy* objects, like Verier and VPI turntables and big amps but speakers like the 400 lb Magicas have such a high center of gravity it would necessitate a very large platform/plate under the speakers to be able to spread the springs out as wide as possible. Nevertheless the isolation, assuming it could be achieved mechanically, would be spectacular. The new Super Stiff Springs are low profile (2 inches tall) so they have excellent lateral stability. It would require about 8-10 SUPER STIFF SPRINGS to isolate a 400 lb. speaker. I estimate the platform would have to be 4x4 feet and could be say maple or Baltic birch plywood. It would be less challenging but interesting to isolate a large, heavy subwoofer using Super Stiff Springs.

My Legacy Signature III's weigh 140 lbs apiece. They sit on a raised wood foundation. They really came into their own when I put them on one of Mapleshade's 2" thick, unfinished maple platforms. The platforms are spiked to the floor though the carpet ... and the speakers are spiked to the platforms. It was very cost effective to do. If I remember correctly, the unfinished platforms were $175.00 ... and I already had all of the spikes on hand. I bought the unfinished platforms because of the cheap price. I wasn't sure they would work as I intended them to work. Now I wish I would have bought the finished platforms from Mapleshade. They're quite beautifully finished. 

Thanks for all your input!

Adding a wooden platform may not be a good solution on my suspended floor so I am still debating between converting the vibration into energy a la Stillpoints or Finite Elements or conducting them away fast a la Star Sound.

There may be a point to isolate the speakers as Tim and Geoff suggested. But I wonder what happens to the remaining kinetic energy stored if you isolate such a big mass like the Sovereigns?

In the meanwhile, I have bought a pair of Sistrum SP004 for my monoblocks (see my other thread about decoupling my mono blocks) that I can carefully try under the Sovereigns first to get a sample how it affects the sound.
I have Stillpoint Ultra SS under my DAC and could buy another set to try them for a couple days under the Sovereigns. If that works better than Sistrum’s approach, I will probably be heading towards Ultra 5 with base, hoping someone with deeper pockets is upgrading to the newer Ultra 6, putting the U5s for sale (wink here).
Has anyone compared the Finite Elements Cerabase with Stillpoints Ultra SS or Ultra 5? It may constitute a viable and less costly alternative. Ditto goes for the Black Diamond Racing Super Jumbo Pucks;  I like BDR for the excellent value/money.

Luckily I have less of a problem in my home theater where the lighter but not-so-featherweight like Duntech Black Knights (only 154lbs each) sit on Symposium Svelte shelves on the wooden floor which is directly on concrete (tight bass).