Jadis JA30 Mk2, how great???

@mozartfan Remember, the typical vid you are watching on YT is of the original Jadis JA30, not the 30Mk2...which is a much newer design and frankly, sounds IME very different to the original. ( as it should, since the transformers and KT150’s are very different). If you heard the original, which is highly likely since there are few 30Mk2’s out there, and certainly not many on YT. ( although i think I may have posted a vid). Then you didn’t hear the new amps, plus, like you state, YT vids are basically meaningless when it comes to actual SQ of the piece in question.
IF you do acquire a JA30, (whatever vintage), i would suggest/opine that you DO NOT MOD IT, like you have the Defy!! IMHO.

Just update the status! My JA80 is coming soon! Now trying the new Diapason from Jadis which sounds as great paring with most mid to high sensiti ity speakers! 

How are the new JA80s?

Fantastic! Never believe the JA80 can be so dynamic! I am not sure how it compares with the former KT88 model which i haven't seriously auditioned before going to the new MKII.  Sound opens up a lot after few months of burning in! I am currently using it in biwiring to drive my Dali Epicon 2 with great satisfaction! Musical, Engaging & organic sounding that drove us to the music. Plenty of power you wouldn't worry about. Regret to own them so late! Cheers!

However, the Diapason is worth every penny too! It has the sweet sounding character of 6L6 tube and it really has those magic from Jadis! It hasn't got the deep soundstage or details as the JA80 for sure but it really worth for only just one fifth of the price of JA80!