I had the 2B SST on demo in my system and although good and very neutral I found the treble a bit tipped up and overall a bit thin sounding relative to my McCormack 0.5 Rev A amp (now upgraded with their later G22 upgrades), so I’d definitely focus on the SST2 as that’s supposedly a bit more refined up top.
That said, I brought my amp to my friend’s house who has a 3B SST2 and both of us much preferred mine as it had better tonality, dynamics, and an expanded soundstage. In short, my amp sounded more natural, robust, and refined despite being the lower-powered amp on paper. I bring this up because this DNA 1 with the same upgrades as my amp just became available for $2400, which is basically the price for the G22 upgrades so you’re basically getting the amp for free, and it’s about the same price as a used 4B SST2. Without hesitation I would jump on this amp as SMcAudio-upgraded amps are considered near SOTA, and you’re basically getting a near new amp as the upgrade basically just keeps the case and all the internals are new and likely done within the past five years. Bottom line — I’m confident this would blow away your Adcom on every level. Just my $0.02 FWIW, and best of luck.