This thread has been very illuminating / instructive. It ought to be required reading for all audio hobbyists.
Klipsch loudspeakers are a known quantity. They’ve been around for a long time and because of that, and because they have always represented a good value, it seems that many audiophiles have owned them at some point in their audio career—especially early on. That includes me.
So there’s a striking degree of recognition among the folks responding to your post when they read your description of how the Cornwalls sound with the Pass electronics:
The amp, you say sounds
"somewhat muddy and lacks a lot of air and grip. The soundstage is very closed."
And the preamp
"removes a lot of resolution and information, without transient attacks and sunken mid frequencies. Instead it brings warmth."
That’s how Klipsch loudspeakers sound! The Klipsch sound is vivid, bold, and dramatic but I don’t think many would consider it especially refined. The Pass gear is exceptionally neutral and tells this truth well.That’s why there’s been a consensus that you need to listen to different speakers.
There’s clearly a lot about the Cornwalls that you like and that’s fine. There’s a reason they’ve been around for 75 years. But you are recognizing their deficiencies and looking for a way to "fix" those shortcomings with electronics that will somehow compensate. This won’t end well.