Sensitivity-Efficiency is volume/power. You get a sense of the PROBABLE amount of attenuation (less or more) you will need when you mix and match.
Frequency response is quite another thing, I suspect your Klipsch Mains will also ’blend’ both volume and frequency characteristics. You don’t want specific frequencies jumping ’out’ or ’in’ from l/c/r. I would try that change FIRST, then go from there.
My separate 2 channel system, ’other end of the room’
https://systems.audiogon.com/systems/9511I use Two L-Pads in each speaker (vary attenuation of mid horn to woofer; vary attenuation of tweeter to mid horn. Hard enough, then VERY HARD: I have to very carefully match L to R
so Casandra Wilson’s Voice doesn’t move L or R of Center, or certain Piano/Violin frequencies shift this way or that, that’s a no no. Takes weeks of decisions playing all sorts of music. Ah, when done, awesome. Don’t forget, this is done IN MY LISTENING SPACE, not some factory average design for imagined unknown spaces.
I just made an offer for one of those Klipsch R-34C Center Speakers (used) for myself. It will be too efficient, my DBX Soundfield 100’s are ’only’ 91, so I will likely be cutting the center channel signal output in the AVR. Except, my Mains are near corners, and use special ’crossfire’ angles (like large toe-in), so who knows? Frequency Blend? I can return it, I’ll risk the return shipping cost.
Back to the old big CRT days, I’ve been happy with the little Bose VCS-10 which fits anywhere, including behind a CRT inside a wall unit with receding doors way back when.
I have more room now that I chopped my big wall unit down, put my Monitor on a Glass Shelf on a 7" Riser I built with some of it’s solid cherry wood, the Klipsch fits, right at seated ear height (no rear ports).
back to attenuation: My rear surround speakers are small directional speakers, Paradigm Micro v.3. I still remember the surprise when I first heard them at 6th Ave. Electronics.
https://edsgoodstuff.com/edscart/index.php?main_page=product_info&products_id=7559laying on their backs, firing up, using the 6" wide space between the back of the sofa and wall behind like a horn, so their efficiency/output is what it is, then attenuated in the AVR. (I stuffed some foam in their tiny rear ports).
All these years I just do the volume adjustments in the AVR, done, good enough, no room correction like you do. I reset occasionally, do the basics, I forget all the damn options, just adjust vol then use either Direct; 5.1 or 2 channel. I occasionally find forced 2 channel sounds better, there's a lot of crap mixes out there, and who knows what studios/cable companies are 'thrilling' us with.
My Single Sub, 1,000 watt Velodyne, is adjacent to me (see photo), fires facing the front opposite, crossover and volume for my viewing spot. Off for Direct 2 channel or forced 2 channel, the DBX have 12" woofers, plenty except Jurrasic Park, Black Hawk Down.
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I hope you have discovered this movie, Domino, with an awesome kick-arse sound track.
https://www.imdb.com/title/tt0421054/
