I've taken a pretty extensive tour of tube amplification over the past 35 years, and am currently running three SET systems with tube pre-amplification. None if this gear is McIntosh, but not for lack of audiophile quality from that brand. That company did suffer a product crisis in the 1980s into the early 1990s, but you can't be too hard on them for that. During the same period, the aural horror of Krell was introduced to us, Audio Research sound got progressively colder and ascetic, and the CD was still finding its way to quality in the entire chain from digital recording to mastering to duplication to playback gear.
However, you'd be hard-pressed today to hear a better amp at any price than a McIntosh MC1201 monoblock pair, and its smaller brothers in the "quad differential" range aren't slouches. The MA6900 integrated is one of the more musical integrated amps of any topology. Their push-pull tube amps are among the best of that topology. And the preamp range gives you a good range of transistor and vacuum bottle options delivering essentially the same balanced, musical, penetratingly revealing sound. I don't find satisfaction in any of McIntosh's speakers, but for some other makers' speakers, there's no better amp than a Mac.
Phil