I said it before, here is a good example of good sounding (or at least preceived sound) amp but bad measure results, and I think plenty of tubes amps will be in this category (even 4000usd are in thi category). I had this amp and as I also mention, to me, was the best soundning of the 4 amps I had at home.
And despite the critics to the YT reviewers, they have plenty of amps to listen and HiFi experience and they still choose this little amp as well regarded, twice.
So it makes you wonder how something that measure so bad can sound good to many?
There is a difference between likable and accurate. A likable amp does not have to be accurate if that's not what the buyer is looking for. Lots of people buy tube amps because they find them to be likable, but very few are as accurate as mid-level solid state amps. We dweebs on audiosciencereview.com prefer our amps to be accurate to be likable. I would not buy the Vista Audio Spark II.