No experience with the Kats, but I built (assembled is probably a better term) a pair of George Short's Rhythm Revelator Signatures about 10 years ago, with wonderful cherry cabinets as built by Lee Taylor. I purchased the speakers broken in and with matched perfect quads, and the 8 gauge air coil inductor crossovers. The physical size of the crossovers precluded them from fitting into the speaker cabs directly (they were built on a single board and weigh close to 35#s each), so Lee Taylor built stand alone crossover boxes (bi-wired capable) which are spiked and sit aside the Rhythms. Unlike the Big Kat, the Rhythms are meant to be placed "away from the wall" into the room. I think they are about 92db. I have loved these speakers and have used both 2A3 and 300B SETs (as well as PP ST-70 clone, PP 2A3, KT88 SET), but they really need the 300Bs if you have significant dynamic range material. They are are in a dedicated 2 channel system with my 300B SETs, not HT. I have never felt the need to augment the Rhythms with subs. Great imaging and sound stage, with all types of music.
I have continued to experiment and build and replace everything else in my system over those 10 years, but not the Rhythms - no need, or desire to do so.
(Well, I have "strayed" for a bit with a pair of bi-amp'd OB Hawthorne Sterling Silver Duets, but I'll never divorce the Rhythms.)
