The tube compliment for some models above has been incorrectly stated. The BAT 30 and 31 use 6 6922 tubes while the 30SE and 31SE use a quad of 6H30 tubes. The Aesthetix Calypso uses a pair of 6922 (6DJ8 work too) and a pair of 12ax7. So if Audfile is looking for models not using the 6H30 tube, the listed candidates is valid. The CAT would be worthy of consideration if balanced I/O was not needed/wanted.
I can not speak about the 30 or 31, but I had the 6H30 based 31SE for 2 years, and it had great "harmonic warmth of tubes". It just has a little bit of a roll off on top which reduces the detail and ambience in this range. This latter sonic character is not at all an issue with the Calypso. But the Calypso does not have the same bloom in the mids. It's one tradeoff for another here.
For a few hundred $$ more than the LS-15 as sold on the used market, the LS5 is a logical choice. Even with stock Sovtek tubes, this significantly outperforms the LS15. With an investment of Mullard or Tele tubes, a replacement of the caps to Dynamicaps, or perhaps a GNSC update, this modded LS5 would be an unbeatable value in the <$3000 or so range.
There is no way anything can be tagged as "best"; such a label has no value. And the only way to truly know what works for you, in the context of your system and relative to your LS15, is to bring home some of these models and do a direct shootout in your system to your LS15.
I can not speak about the 30 or 31, but I had the 6H30 based 31SE for 2 years, and it had great "harmonic warmth of tubes". It just has a little bit of a roll off on top which reduces the detail and ambience in this range. This latter sonic character is not at all an issue with the Calypso. But the Calypso does not have the same bloom in the mids. It's one tradeoff for another here.
For a few hundred $$ more than the LS-15 as sold on the used market, the LS5 is a logical choice. Even with stock Sovtek tubes, this significantly outperforms the LS15. With an investment of Mullard or Tele tubes, a replacement of the caps to Dynamicaps, or perhaps a GNSC update, this modded LS5 would be an unbeatable value in the <$3000 or so range.
There is no way anything can be tagged as "best"; such a label has no value. And the only way to truly know what works for you, in the context of your system and relative to your LS15, is to bring home some of these models and do a direct shootout in your system to your LS15.