Armstrong had quite a few between 37 and 40. Have to look that up. edit: 26 of 27 of his opponents in ´37 ended beeing (T)KOed. Probably of a higher quality than Streibling´s too.
You're right... while there were several good names (including 3 world champs) among Armstrong's ko-victims in '37, the same can't be said of Stribling's opponents in '28. With very few exceptions they were mostly nobodies - and 11 of them had yet to score their first pro win, when they entered the ring to face Stribling! So Armstrong's '37 was easily much more impressive than Stribling's '28.
I'm not sure, but that may put Clark in 2nd place after Stribling. hh would probably know, if this is the case.
I'm only going by BoxRec, he won his first on points then had a mental 1958, all KO's, opposition less than stellar of course