i don't know what drivers you plan to use but i've heard these horns with JBL 2451 fitted with truextent be diaphragms and despite a need for an 1.5"->2" adapter it's truly a great sound - even in a real nearfield situation (under 2m from them) they integrate wonderfully, no beaming, no any horn nastiness one can experience with lesser designs. i was really caught by surprise as they are simple exponential profiles and these days other profiles gets more prominence and exposure. could be also it's a perfect synergy between horn and driver - which matters more than a horn itself - but KH-55 is high on my personal list.
Gordan.
Speakers: Oris Swing MkII
Amps: Thomas Mayer 300b/ Hiraga La Maison de L'Audiophile 20
Preamp: Silver AVC by eng. Ferenc Lazar
Phono Preamp: Shishido LCR by Solaja Audio
Decks: Garrard 301 Martin Bastin reworked/plinthed with Fidelity Research FR64fx
Garrard 401 in eng Ferenc Lazar solid wenge plinth with SME 3012/2
Cartridges: SPU Spirit/ Koetsu Black revisited by eng. Salai/ Miyajima Shilabe
Step Up Transformers: Tango MCT 999/ Ortofon T-5000/ Lumiere SUT
Digital: Shigaclone by eng. Ferenc Lazar with Lampizator Amber II
Wires: of sufficient length