I have been through the creating a main living space in the House to be an improved environment for listening to the end sound from both music replays and end sound from audio visual.
If the most comfortable seat is wanted to be used and it means the moving around of furnishings to achieve this there will be a minimum of a raised eye brow from an observer with an interest in the room. There are fold away chairs that are very comfortable and suited to long periods of seating, look at the Camping Market or Carp Fishing Market.
These are compromises to be made between two people, there is nothing I can say to fix such a situation.
High Pitched Reflections of Windows are reasonably easy, close curtains or blinds, increase weight of material for curtains, or add curtains to be used with blinds.
Hard Floor reflections are again easy, add something soft, it does not have to be permanently seen, and does not have to be overly sized. Choosing the density to align to the room will be the trickiest bit to achieve.
Absorption is harder to manage, as it is most likely taking place in a non symmetrical happening, and soft furnishings are most likely to stay. Balanced Absorption can be improved if a dedicated Wall Panel or Two is produced, a partner can even select the Canvas Artwork, that would conceal the purpose of the Ab' Panel and leave only evidence of wall hung art. The Partner will need winning over to accept the locations selected for placement.
Bluetak Helps as the room produces less noise, other masked noise will manifest, ratting Picture Frames and Ornaments, each easily tamed by a few pea size Bluetak Pellets squashed in behind or under the offending rattler.
Once that side is done, if the Room still feels there is a upper frequency Roll Off, the Speaker Xover might need to be investigated for a little work carried out, to push forward Upper Mid's and Highs and Lean Up the Bass. Alternatively if there is seemingly too much emphasis on the Upper's Rolling them Off a little might be just enough to create a Coherence through the frequencies. Tweaking Xover's on Speakers not in Warranty Period is a common practice.