Have you updated the firmware, so it had "Open" speaker tuning?
Of course. I'm anal about updates & I go through every possible amp/cab/eq/setting possible.
Look, I'm a huge THR fan. I played my 10X each and every day for five years. Wonderful piece of gear! But the Kemper & the Yamaha are two totally different beasts. The THR is basically a wonderfully simple, transportable thing of beauty. But Yamaha overpriced it, and, imo, ruined the high gain amp models. I mean, c'mon - four of the tones are from the same amp, a supposed 5150iii. There's only so many tones in the thing, yet they put four of the same amp in there? That perplexes me.
*Edit* Look, if the new THR works for you, that is all that matters! Sound is subjective. I can tell you the Brown 2 is the best thing Yamaha Music has ever created. My god that amp model is truly incredible, but that took months to get right. The Kemper? Literally seconds after turning it on, my rock-filled brain went "Ummm. Yeah. Ok. Haha. The THR10X is going up on for sale. Like, now."
Five years with an amp & the K comes along and just TKO's the THR. *ding ding*