Innersound ESL-300 is a very good alternative to Pass. Grainless, smooth and dynamic. It seems to impart a slightly stronger foundation to the music and is very homogenous. Perhaps slightly less light'ish sounding too. But that takes nothing away from the Pass because they are very good amps too. The Pass X-series is slightly more incisive through the midrange and treble area. This is an advantage on strings. Aleph series is a little too soft in this respect.
Someone above mentioned the Monarchy and, this is also a cost competitive alternative. They sound very similar to the Aleph series with just a touch more incisivness.
I still think the Innersound ESL strikes the best balance between solid state and tubes. But, if you listen to a lot of strings and chamber music, the pure honesty of the Pass X-series (or Aleph for that matter) is hard to beat.
Someone above mentioned the Monarchy and, this is also a cost competitive alternative. They sound very similar to the Aleph series with just a touch more incisivness.
I still think the Innersound ESL strikes the best balance between solid state and tubes. But, if you listen to a lot of strings and chamber music, the pure honesty of the Pass X-series (or Aleph for that matter) is hard to beat.