sound that I really dislike
That's the most important part of your post. It's a sound that
you dislike. But will someone else dislike it? I will suggest that we all temper our descriptions to include what our own taste might be, as you have done in describing what you are hearing from RCA 6080s or 6SN7s. I don't necessarily disagree with you, particularly about a 6SN7 sounding a little lacking on top. But it's a very linear tube, and it has a great midrange. Some folks absolutely love the sound. After 25 years at this I know for sure that my Crack amp might sound like crap to one person, but not to someone else.
The original idea behind this kit was to offer a cheap way for all of us to roll tubes and form our own opinions. I still think that is the best approach. I'll also suggest that people stop paying stupid money for tubes. I buy tubes on ebay all the time. Not the overpriced ones. IME about half the sellers know jack shit about what they are selling. Caveat emptor. The law of diminishing returns applies heavily. If you see some 6080/6AS7 variant for $400 on ebay, run the other way. It might sound better to you, but it won't sound 26.66 times better than a $15 one. If we all start paying $400 for a 6080 tube pretty soon a Crack kit will be a grand.
Oh yeah, and all of this opinion is useless if you don't say what headphones you are using to form these opinions. Let's be logical here.