Glad to hear you’re happy with the QLNs but can’t say I’m surprised given their glowing reviews, and I think they look pretty cool too. I think the LTA will add just a hint of more upper octave transparency and detail and may be a perfect addition to your system. Looking forward to your impressions.
Also, I’d recommend trying a pair of SVS SB1000 Pro subs. They’re only 13” square so aren’t visually imposing or take up much space, but despite their small size they’ll get you down to an honest 20Hz (-3dB). Plus they offer onboard integration software you control with your phone so you can easily dial them in from your chair. And all this for only $1100 for a pair, and they offer a generous 45-day, risk-free trial including shipping both ways, so why not? Remember, adding subs is not just about bass but also greatly enhance imaging and soundstage. My guess is once you hear what they can do you won’t mind their diminutive presence too much. Just my $0.02 FWIW.