H&K and ENGL
I won't be of much help I suppose, but anyway.
I have both an ENGL Rackhead 850 and a H&K Triamp MK I. I admit that I got both of these used for cheap, as I live in Germany, and that besides those I have not really that much experience with amps.
FWIW, the Triamp is the MK I Combo with 2 G12H-100 speakers and 6L6s in the poweramp. Amp 1A has a really shimmerimg beautiful clean, 1B can get you in bluesy territory. Amp 2 has a marshally vibe going on, 2A being quite bright, 2B a little bassy, almost too bassy for my ears. Many have stated that they have no use for 2B, but I think it's still usable. Amp 3A is not a really high gain channel, I miss a little sustain with it, but it's a good heavier rhythm channel. 3B is really the lead channel, but it has its own thing going on soundwise. I am hesitant to compare it to any other amp because of my lack of amp knowledge. The amp is of quite good quality, altough the one I bought used had a problem with the clean amp (Amp1), it was really quiet in comparison to the other 2 amps, but that was easily fixed with some soldering at the input stage (a cable was a little loose). The schematics are available online and the support from H&K in Germany was fast. Maybe that is already bad news for you, but I have not heared of many problems with H&K's tube amps.
The ENGL is a early 90s rackhead, EL84 based with 2x35 watts. It's my "main" amp (out of 2, haha!). 3 channels, shared EQ. No brilliant cleans, not really high gain. Built very well. A great amp for rock, not metal. Most modern ENGLs seem to be made for metal, although the Blackmore Sig and the Special Edition are very versatile as far as I've heard. But I didn't play either of them.
I played an ENGL Screamer 50 combo once and was impressed with the sound and the gain that thing had. I don't remember if the EQ was shared. It was built well as far as I could see.
Maybe anyone can use something I wrote.
Regards,
Jochen