A21 isn’t cutting it. sibilence and not enough juice to drive the woofers sub-less.
The JC5, which I’ve demo-ed with the 702s, does a great job at it and is my runner up as it stands.
I’m betting you demoed those in a different room, in which you shouldn’t compare them.
Every single modern B&W speaker has increased output at 10kHz,
including yours. So, experiment with toe-in amounts or even no toe-in.
As for bass, your room is large (3000 cubic feet if only 8ft ceilings). Audioholics describes for that size, the speaker must be able to output 115dB minimum between 31.5Hz to 63Hz at a 4 meter distance, I can gaurentee you that your speakers aren’t able to hit those numbers, even if you fed the max wattage it can handle (300W, even though I doubt it won’t have audible distortion in the bass when fed over 100W).
So yeah, your speakers are physically incapable of having reference quality bass in your room, so I would suggest crossing over at 40Hz or 60Hz, even though I know you said you don’t want to.
If you are not listening at reference levels, then maybe you are hearing less bass due to the Equal Loudness Contours, our ears hear less bass at lower volumes, in which tone controls/EQ/DSP will adjust this.