I have both the Seismic Pods as well as the Seismic Vibration Isolation Platform. They DO sound similar, but (and I don't have to choose, but I know you do) I would try the Vibration Isolation Platform. I have found it to be excellent, especially under turntables, but just as good under say, a line conditioner.
Might I suggest you see if the Critical Mass Center Stage 2M footers can be used underneath speakers of that weight? They are not simply "excellent footers," they are
magical footers. I defy ANYONE to put these under a component, wait
10 days for it to stabilize (I call on the ghost of William Shakespeare for help: "Aye, there's the rub") and not be drooling 10 days later at the transformation. And yes, if you listen to it at Day 4, you might recoil at how confused your systems sounds, but there it is. Now, I expected GREAT. I did not expect The Second Coming. (That's only a slight exaggeration. I understand Soulution uses these on all their electronics (might be just a rumour, but it didn't sound like it was). I would get Critical Mass for an application before I ever purchased a component. Oh, wait, I've already done that!
If you can get these under your speakers, you'll be set. But if not, the Seismic Isolation Platform is an alternative to look into. And you can change the footers on it to adjust for the weight of whatever you place on it over time. I started with Iso Pods (on the isolation platform) that could handle 40 pounds, but now I used the 60 pound isolation feet (again, attached to the Seismic Isolation Platform). Between 4 footers, your speakers should be fine. That is 60 pounds
per pod. So, 240 pounds total, and strong enough for your speakers.
So, first choice is Critical Mass (yes, I know: you didn't ask about those! But I thought you'd like to know), then the Seismic Isolation Platform, then the iso pods. It just occurred to me that the advantage for the isolation platform is that it's a heavy plate of steel, so it's flat. Easier to get speakers on and be certain the speakers are level, than the iso pods, which are individual, and might be a tiny bit "springy" underneath speakers.
I hope this helps. And, of course, there is Townshend Audio, who are very helpful.