The human mind is bad for comparing sounds.
The mind/ears can compare sounds very good when two different sounds are played in a short time - works bad if a few seconds are between playing the first sound - and fails to compare sounds we heard some days or even week ago.
Yes, its great to have some fine tube amps in the same room with the KPA - sometimes when I play the KPA - and dont like the sound - I compare with the real thing ...
... and often I find I dont like the real thing as well - there are many reasons for not liking the sound: tiered, bad mood, bad weather, flew ....
In general I found that I like both playing the KPA and playing real tube amps - and the KPA with great profiles via a large FRFR system sounds as great as my tube amps.