In my opinion there are two main acoustic challenges presented by small rooms, and these are really the same issue just different parts of the spectrum.
Most obvious is the increased boundary reinforcement in the bass region. This can be addressed by tailoring the output in the bass region to take this boundary reinforcement into account.
The other main issue is the over-abundance of early reflections. I subscribe to the school of thought that says early reflections tend to degrade clarity. One solution is to use fairly directional speakers and deliberately position and aim them to maximize the time delay between the first-arrival sound and the onset of reflections.
For instance, your Hornscalas have good directional control. If you set them up along the 10-foot wall, not too far apart, and toe them in at 45 degrees (such that their axes criss-cross a foot or two in front of you), the first sidewall reflection of the left-hand speaker would be the long bounce off the right-hand sidewall, and vice versa. You’d be sitting pretty close to the back wall so you’d want aggressive absorption on that wall behind your head. You might want to give your Hornscalas a try with this configuration before investing in anything else, to test out this theory if nothing else.
Other issues that a small room tends to have include lumpy bass in the modal region and constrained soundstage size. I think those issues can be mitigated as well through some rather unorthodox techniques. A distributed multi-sub system is very effective at smoothing the bass in the modal region (and smooth bass = "fast" bass), and deliberately adding a little bit of late-onset reverberant energy can reduce the "small room signature" that is superimposed on top of the acoustics on the recording. Let me explain:
The ear/brain system judges the room size by the time lapse between the first-arrival sound and the "center of gravity" of the reflections. By adding some relatively late-onset reflections, we can push that "center of gravity" a bit and make the room sound bigger than it really is.
Feel free to ask questions about any of this, as most of it is rather counter-intuitive.
Best of luck with your quest.