Vibrating floors are a two-way street, eating certain enery and pumping back/increasing other energy, if only as the "in the shadow" effect. I would not bother to try to math/model it when emperical testing will tell me anything I want to know about it. But it certainly warrants investigation, and I would be surprised to learn that you are unable to discern differences in the floor tension, once you are operating FR. If you are still unable to tell a difference, there may be some other issues to attend to prior to attacking the floor.
Generally, one places jacks under beams that run perpendicular to floor joists, for a +/- "whole floor" strengthening aproach. However, Jessie is correct in saying that a jack can also act as a ground path, so placing them under a given spot can have a particular effect.
Romy, if you ever said whether the joists below your listening room are already insulated and/or sheetrocked/plastered, then I forget. However, you might want to re-visit what has already been submitted on this, since there are some good ideas there, already.
Getting the floor tight is basically just another way of getting control over one more variable; and who wants more variables in the quest for decent LF? Tightening/grounding the floors should make it easier to set up and dial in your LF. And unless your new house is freakishly overbuilt, it will also ensure that your 1,500 pounds of equipment do not permanently deflect your listening room floor joists, causing poor little Koshka to roll down into the new trough when she falls asleep listening to music.
The only case I could imagine where a grounded floor would not not outperform a pumping floor is.... OK, I can't think of a legitimate case, but I could imagine a case where spurious gain at some room resonance mode was somehow found to be "desirable" in augmenting a particular system deficiency. However, I might as well add here that I do not hold the view that one way is as good as another to damp peaks and fill in troughs for a flat chart.
Generally, I think it is good to trim back from too much energy. What a nice "problem" to have! Still, I generally don't like, and I generally avoid, weird peaks.