The K-horns are *very* room dependant in their performance in all regards. In the right room, the bass is phenomenal - in the wrong room, ick!
Keep in mind at all times, this was a speaker system designed and intended for *monophonic* reproduction - all there was at the time! So, getting them to image is all the more room dependant (see comments below, for options)
Klipsh used several midrange horns, imho the best of the lot was an earlyish one that was almost as deep as the cabinet and iirc was kind of a black molded up affair using some sort of heavy dead fiber boardish stuff...
You can safely and quickly move to replace the icky EV horn tweeter with some sort of SOTA version without any fear.IMHO, that's the weakest link...
Immediately change all the xover parts for modern good ones... use polypropylene caps and good quality air core coils...
The throat area of the bass horn can benefit from replacement with a much stiffer, heavier material. Corian comes to mind. I know one person who machined it out of 1/2" thick steel. And it did wonders for the bass in terms of clarity and tightness!
There is some question as to the proper throat size for the woofer (there were several woofers) and the original article in Speaker Builder was *wrong*, the follow up was more right... you can consider trying a more modern driver in the hole, and also recomputing the throat size and dimension...
The K-horn bass cabinet *should* be flush to at least two surfaces, usually the corner (3 surfaces) for proper loading. It is feasible to place the K-horns on their side and against the floor/wall
boundary, although the loading will be slightly inferior. In such a case it is "legal" to bring out the mid horn and tweeter for better placement in terms of dispersion and imaging.
The *good news* is that you can drive the thing with very low power, certainly for the mids and highs... I think you want a nice p-p 300B amp for that... For the lows you may or may not want a low DF amp, depending upon how the woofer you have actually sounds subjectively in the room - if it is a bit "woolly" then maybe a SS amp is in order - although you can mess with the horn by lifting it up off the floor a bit and change the loading slightly and the room coupling.
IF I got one to work in my room in terms of *bass* I think I would probably go out and equip myself with some really great and separately enclosed kick-ass horns and compression drivers for the mids and highs... the K-horns (especially the later ones) are nice entry level stuff in terms of horns, but not really smooth and nice as some other things that you can either build, scrounge or buy...