There are several Klipsch (or klipsch-based) systems in the house that I believe most would say sound better than stock Klipschorns in my rooms. Most revolve around the K510 and/or K402 horn. For the sake of brevity, and to stay on topic, I'll confine my ramblings to the Klipschorn with passive networks.
For several years I had three Klipschorn systems in the house. Scooted back and forth several times amongst the three rooms. Stock component '04 Mahogany Khorns with enclosed backs, a '67 Walnut in a mono system, and a pair of '68s in Walnut, which were my experimental pair. With the K400 '68s I played with multiple crossovers (SuperX, ALK) as well as the A and AA with perhaps a half dozen capacitor (Jupiter flat stacks, Jensen PIO, etc.) changes. The K400 came out and Martinelli horns went in with solder lug K-55s and then A-55G drivers. Back to the K400s for a few weeks. Then Eliptrac 400 horns with Faital HF200 drivers went in. A similar approach was taken with tweeters with the JBL2404, Beyma CP-25, and Eliptrac HF moved in and out . A significant number of amps, preamps, cd players/dacs were shuffled in and out during this time but always an apples to apples comparison was used to evaluate simple changes to the systems.
None of my rooms are very good Khorn rooms. To alleviate the room shortcomings several arrays of absorption and diffusion were tried to maximize the experience. I have listened to khorns (K400) in one exceptional room and another system in an extraordinary khorn room. What a difference it makes! What took me some time to prove to myself was that I can't trick a poor room with treatments to the level of a room with great fundamental dimensions.
I've owned a pair of Volti Khorns in Koa for a few years now, usually running with a LaScala (same veneer) as a derived center. There isn't much Klipsch left of the Khorns outside of the plywood construction. The tophats have the first two production V-Trac (FC-260/BMS 4592) horns Greg made along with Beyma CP-25 tweeters and VTK-400 networks.
I can say with certainty that my ears have never heard Khorn's (K400 squawker) with any combination of variables (networks, source components, etc.) sound as good, or connect me with the music any closer, in my rooms, as well as what the Volti Khorns have. I can put many combinations of the Martinelli horns and Eliptrac horns in the same tier as the V-Trac. This is not a case of the 'this is what I own so its the best' nonsense that plagues many discussions on comparisons but my feelings some time after most of these systems have found new owners.