Yes, it will help more with higher freqs vs. LFE.
Horse stall mats and rubber mats in general are helpful, and they will mitigate some of the sound. However, loud and deep bass is going to pass through easily. It's really tough to say ahead of time if you'll be satisfied with the result. I can tell you IMHO, with a 2nd floor theater room, the floor in the HT room is the biggest challenge. Your best bet with that floor would be to rip out the sub-floor and de-couple the room's floor. I know that is a huge pain and easier said than done.
Presuming you don't do that, even with a floating floor, you're going to get considerable pass-thru sound (LFE in particular). Lay down a double-layer osb/rubber/osb/rubber combination (or similar) if you have the means. Anything you do above and beyond a normal floor will help. Thick carpet pad would be helpful as well. Just don't expect a miracle.
You'd have to contact Kinetics and ask them if they have a reseller local to you, or if they would sell direct. It's not cheap, but thought I'd throw that out as an option.
Why would ripping out the existing subfloor and decoupling a new subfloor from the joists necessarily be better than leaving the existing subfloor and decoupling it from a secondary subfloor laid over it?
My impression is that the primary reason not to put down a secondary decoupled subfloor is that I've got some untreated walls that will create a flanking issue, especially for lower frequency sound.
And if I had to guess, putting down rubber-second subfloor-rubber-third subfloor would yield only marginal improvements over the more basic rubber-second subfloor. If anything, if I were looking for a more involved floor treatment, I'd think rubber-second subfloor-Green Glue-additional subfloor sandwich would be a better bet, creating a single more massive suspended subfloor and damping it to boot. Anyway, this is all hypothetical, because if the case for a simpler floor treatment is tenuous, it's all the more so for a more involved treatment.