Jadis JA-30 vs JA-50 need opinions

Ditto! Looks like you "get" what the Jadis sound is all about.

I'm going from years back, as I haven't kept up with current production, but I believe the JA 50 uses KT90 tubes, where you could use EL34s, 6550s and KT 88s with the JA 30s. IMHO the Jadis amps using KT90 tubes sound perhaps cleaner than the other types, but ultimately uninvolving in comparison. With the right speaker, the JA 30s I have heard could be magical, particularly with vintage EL34 tubes, but they probably will not give have as much control on the bass as the KT 90s do. KT 88s in a JA 30 might be a good compromise between bass control and midrange magic.

While the JA-30s certainly won't have the power of the Defy, in my view they are the more refined amplifier by far. The sound of the JA 30s would be more akin to the DA88 thsn the Defy, IMHO.

In listening to the JA30s, keep in mind that the brands and types of tubes used can have a decided influence on the sound, especially the small input tubes (I prefer vintage Telefunkens, but others have their favorites as well). Since the 30s can use EL34s, KT88s and 6550s, that choice will also influence the tonal balance and bass response that you hear. Finally, you should try to listen to them with either your speakers or something similar in sensitivity, impedance and frequency range.

With respect to reliability, with the distributor and good repair shops nearby, I think you'll be fine. The only problem I had with my JA80s in my ten years with them was due to some modifications I had done to them, so I can't blame Jadis for that. The amp can eat up output tubes, though. I found that the best and longest lasting tubes in my JA80s were vintage Gold Lion KT88s; 6550s and EL34s tended to go bad and start blowing fuses after a year or so.

Overall, I found that when I first listened to the JA80s I bought there was nothing about them that really stood out and grabbed my attention, it was more a general feeling of "this sounds right". I think that if you get that feeling, then these amps may be the ones you should buy.