The k-tre is an incredible amp, I've sold off almost all my other amps since I got one. It's a more modern voicing then the earlier knuckleheads though so I guess it depends on what type of tone you want.
For what it is worth, I have a KHR 55 and I absolutely love it. I also have a Duarte and love that too, but it is completely different than the KHR. That said, I don't even use the third channel on my KHR so I might not be the best person to judge by. My amp can get very good high gain sounds, but that is just not my style at all.
KTre for modern high gain. Very tight with more emphasis in the lower mids and TONS of gain on tap. Not my cup of tea personally but sounds like it would be right up your alley. Buy used and save a ton of $$$.
I think the k-tre is tighter and it definitely has more gain. Way more. It's been a while since I've played the kh2 but if I recall it also has that aggressive voicing like the k-tre but less gain and less low end. I would (and did) go for a k-tre and it's my number one amp.