My Crack came stock with a RCA 6080, it's actually pretty good. I think I prefer it to the RCA 6AS7G that I have. I have a TS5998 coming in on Friday so we'll see how they hold up.
There was a listing on fleebay for ten assorted 6AS7G's and one TS5998 for around $95 BIN. Hesitated for a bit because the seller didn't list any test values, and then it disappeared
. Would have been fun rolling those tubes to see the differences.