I usually like multichannel amps. However, I usually find the channel that I like the most, and rarely touch the others, LOL. I do value a nice clean channel, but 99.9% of the time, I'll be playing on a fat, grindy, chunky high-gain rhythm tone.
I like Rectifiers' red modern mode set to bold and diode rectification. IMO, that is the Rectifier sound. Vintage and pushed are nice, but IMO, if you want those kind of sounds, there are other amps that do it better. Also, I boost them. Otherwise, for the stuff that I play, unboosted Rectos are kind of unusable.
I also like a 5150III's red channel. Many people swear by the blue channel. I don't. I find it dry and not very gainy. Also not as fat and chunky as the red. No boost needed on the red either. The clean channel on 5150III's is also nice. But I don't really play cleans.
Kind of controversial amps, but I do like Kranks as well. I used to have a Rev Jr. that sounded like crap like at loud full-band volumes, or at bedroom volumes. But it recorded super nice at moderately loud volumes. Needed a boost as well, though. Not as high-gain as you would think.
I honestly kinda like amps with some "ugliness" to the high-end. I guess you could call them that. Maybe not ugliness, but some agression. I find a really abrassive voicing to the high-end really translates well to giving high-gain amps some character in the mix. I guess I do like me some 90's Swedish tones, though. So maybe that's where my appreciation for such high-end voicing comes from. I've never tried a Diezel, but based on everything I've heard from them, I don't think I'd be happy with the dark/smooth voicing they seem to have.
About the right speaker cab, I agree. I do also agree that a Rectifier will sound like a Rectifier no matter what cab you plug it into. But it will sound radically different if you plug it into a Marshall cab with Greenbacks vs. the Mesa OS Recto cab with V30's. Like, really radically. To the point where you will have to redo your settings completely.