dcevans,
Thanks for asking Teajay for some specific comparisons between the speakers to start with. While Teajay said he would be doing a more in-depth review, I'm glad he answered our questions now.
By the way, I doubt I am a more dedicated audiophile, I just happened to have a portion of our walkout basement I could remodel into a listening and movie room (heavy emphasis on listening).
I also wanted to respond because we currently have similar speakers. The Heresy III’s you have are very fine speakers and I've been listening to various models since the 70s. I run Klipsch Forte I’s from the late 90s modified with Bob Crites’s crossovers and titanium tweeter diaphragms as well as older vintage Heresy midrange horns and compression drivers since they are the exact same one’s used in the Forte I’s, but are are of higher quality vs. the period my Fortes where made. (Klipsch, like other companies mentioned in this thread, used other manufacture’s drivers and changed them based on availability, cost, etc.). These changes brought more clarity and control the midrange and upper frequencies while better integrating the already deep and tight bass. Of course your Heresy III’s already have all the current improvements.
If I didn't feel some more depth, richness, etc., could be added to the midrange based on higher end horn speakers I’ve heard, or the reviews I’ve read about Tekton, I would be quite satisfied given the investment made.
While horns may not end up being the best match for you, here’s what has worked for me with the Forte I's.
While I’m not familiar with how you have situated the speakers in your den, lifting my already 36” high Forte’s up another 5” to bring the tweeters to ear level gives the best detailed and open sound. I also have them toed in so the horn is pointing a few inches outside of my ears in my listening position — rather typical with horns.
The Heresy, while the first Klipsch speaker not to have a horn loaded woofer — hence the name, since someone said the design was heresy — is still designed to be used near a corner or wall. But playing with placement after attending to the tweeter’s position can still help. The Forte’s have a passive radiator in the rear and require being about a foot and a half away from wall boundaries. This is something you would want to consider with the rear ported Fritz Carrera, but I’m not familiar with that speaker myself, so hopefully someone else can address that for you.
You also mentioned the Heresy’s sound better at louder levels. Mine can sound a bit thin at lower levels, but rising the tweeters did help with that. I really got into stereos in the mid/late 70s during college while working part-time at a dedicated stereo store (back when they existed) and graphic equalizer were very popular. A restored/upgraded SAE Seven that I am not ashamed to use helps give a fuller sound when adding a touch of bass and high end (actually subtracting what you want to de-emphasis is best). Tekton’s ability to help our midrange focused hearing at lower levels does sound intriguing though.
Some of the coloration issues in horns is helped with tube amps, and your amp will certainly make the most of tube’s advantages, so your comment about tube rolling is worth looking into (and fun). As you probably know, the greatest sonic change typically takes place rolling the tubes used in the front end, 6SN7’s I believe in your case. While subjective, basically you change tubes with characteristics to either add warmth OR give a more analytical sound, so decide which direction you’d like to go based on what you’re hearing.
You mentioned about giving up some resolution to help make poorer recording more tolerable, so if you want to use the den’s sound system to enjoy these records, going with warmer tubes and/or speakers can help mask their short comings.
Finally, while your room is primarily a den, acoustic treatments still play a big roll. A friend who has Focal Aria 948’s, (amazing speakers in their own right), and was familiar with my Forte’s before the listening room was build and treated said he was surprised horn speakers could as good as they do. He has some nice wood covered acoustic absorbers and diffusers from GIK that are both very effective and aesthetic, so see what you think.
Didn’t mean to ramble or get off topic, and you probably know this stuff already, but hope some of this helps. Good luck.