Room Problem Improvement Question: Over a Garage

My current listening space is a second story room located over a 3 car garage and about 18-20'x30' that is a 2x4 stick construction supported by 2 microlam beams that run over the garage, parallel to the cars parked below, supporting the joists and 3/4inch subfloor beneath it. The surface is thin pile carpet with a thin pad under that.

The previous owners finished the space themselves and as such did not insulate at all between the floor joists to the uninsulated concrete garage underneath. The Garage ceiling below is about 10 ft and has blueboard with plaster over it.

Acoustically speaking, this is not a bad space, with ceilings being around 8' and is actually one of the better listening spaces I've had in my last 3 houses, even though on the left wall is a 45degree slant coming out around 3 feet running a good part of the length of the long wall next to my left speaker. I get great depth and fairly decent imaging and tonal balance, but I have floors which leak a considerable amount of bass and are INCREDIBLY SPRINGY! I can be walking softly on the other side of the room and my lead and sand filled Billy Bags rack cannot stop my needle from bouncing on a record! Also, I'm concerned about room nodes and overwhelming the space with all the sympathetic vibrations/resonances going on all at once, and even some of the reverberation from sound leaking down, bouncing off concrete then coming back up.

I am getting some very full range very dynamic and very heavy loudspeakers delivered in August and am concerned about this enough to begin getting quotes from builders for some kind of fix before their arrival.

Some of the ideas I've been given include:

-Spraying Icynene foam between the floor joists from the garage below to fill the spaces that are uninsulated

-Placing another layer of subflooring with a product called Advantech, which is a type of OSB that is far heavier than 3/4" subfloor then resurfacing with either:

a) Hardwood or
b) Another carpet or the same one if it can be salvaged.

- Just placing hardwood over the 3/4 inch subfloor and call it a day.

- Move the party to the 3car garage below which would entail getting HVAC systems,carpeting as well as walling off my garage doors and dealing with my wife having to park outside during the cold snowy winters and rain.

Any ideas on what to do in this type of a space? Has anyone had a similar problem with a room over the garage? The span is so long (23 ft) that I think it may be a lost cause and that adding subflooring ($2k) plus carpeting ($3k) may not even do the trick since it may be the floor joists below that are causing the problems.

My question is if anyone out there has done this type of project, what were the results and should I give it a try or just wait and see what happens when the new speakers arrive in August? It may be impossible to move them once they are in place. I'm also concerned that if I use wood flooring the room may become too bright sounding by not having the wall to wall carpeting currently in the space.