Well, up to this point I've been trying to help with your stated problems, which were a) the need for subs, and b) addressing room modes. Starting from scratch is a whole different ballgame and order of magnitude greater expense.
So let's play that game. As always, it starts with the room. Yours is small and with similar dimensions, so problematic in terms of modes, and lots of room influence overall because of short distances involved. So if you can accommodate it, at least dual subs would be beneficial. Speakers with really smooth power response are key as well.
You appreciate it loud, so you want banger speakers, although the small room works in your favor in this case.
And you seem to listen in different spots rather than having a dedicated and specific mlp, so you want speakers with uniform response, and not only horizontally but also vertically, so they don't change whether you're sitting, standing, working out, etc.
All those considerations suggest possible choices that would check all the boxes. You mentioned Genelec. Good idea, if not for your wallet at least for an initial case study of speakers that check all the requisite boxes on your list. They do have models larger than nearfield monitors that would get loud. They use some of the best coaxial drivers, with really uniform response horizontally and vertically, so they're both room friendly and devoid of the "head in a vice" tiny sweet spot. They would sound good throughout the room. They are a thoroughly modern, fully active, dsp corrected designs with sota performance. Those would check all the boxes.
But they're kinda ugly, and not the only girl at the dance.
I would suggest taking a long, hard look at what Sigberg has to offer, they would check all the boxes too. Their "small" bookshelf models are real bangers. Good coaxes, fantastic performance overall, fully active, huge dynamic range, fuss-free sub integration using their subs, no extra processors or AVR upgrades required.
[edit: Ok, ok,
THIS is the Sigberg setup I was thinking of, and whew, not cheap. That might keep it in the "case study" zone rather than a realistic option, but it is a very good case study to look at. Maybe you're wealthy enough for that. If not, what aspects are you willing to compromise on? SPL is the easiest compromise, as there are many less expensive speakers with excellent performance that would work well in your room/situation, they just won't get as loud.]
Compare such approaches to your Monoliths, which have relatively atrocious power response, particularly vertically. That, combined with the mode issues, means you get the sort of experience you've described upthread (sounds kinda ok in that one specific spot, but terrible elsewhere and huge variability throughout the room).
I guess it's up to you which path to take. But, no, don't get a lousy soundbar, please, for the love of music, don't do that!
