@nasaman I certainly echo Charles’ view on coupling caps. Along those lines, I’d prefer you upgrade to a superior platform first. Then, dial in the tubes and coupling capacitors as time passes.
I’m sure you’re right about that YT video of the Air Tight and B&W bookshelf loudspeakers. Cayin really made some excellent amplifiers. But I believe when you move to something like an Air Tight, Jadis, VAC, etc., you land on a destination piece, and those products will make that apparent to you in short order. In other words, you buy something that’s meaningfully different from the vast majority of what’s out there. Once there, you can maximize performance around that platform.
In terms of reliability, as someone who’s owned a DA60 for more than a decade along with two other integrateds from the company, I can say the Jadis DA60 or DA88S come in about as rugged as anything you’ll find. I had to put mine in order when I bought it, but it provided me a laughably cheap on-ramp to the amplifier. After I fixed it, I’ve never encountered an issue. Like so many tube amplifiers, apart from the chassis and the Jadis transformers they wind themselves, and set them apart, every component on the amplifier is something you can easily source from any of the ubiquitous parts suppliers. And like 99% of tube amplifiers outside of the SET world, it uses the Mullard long-tail pair driver circuit, nothing unusual, difficult to understand, or work through. Finding a tech to get it back on the road should prove no trouble. But I want to say the same thing about the Air Tight and the VAC products, though I believe the latter employs printed circuit boards, which some may consider a bit more "proprietary" in terms of a design than a hardwired product, but still more than workable