comparison between SS Spectral and LAMM tube amp

The best solution with any tube amp is to match it with a high sensitive & simple X-over designed speaker. I listened to endless Systems where the owners said they are great but at the end of day, it was nothing special... A lot say, Wilson (for example because they are rated with 95dB) & Lamm are great, but it isn't.
You will have nearly no control in Bass (it is ok, but nothing special), the higher frequencies have no life or power (this is based mainly with problematic X-overs or aggressive tweeters found in such speaker designs). In a way, these speakers will never come to'life'.
This is simply based on the no. 1 fault from audiophiles: Matching expensive with expensive and the result HAS to be great. Mostly Boring. Mildly said. But a lot will have a different opinion.
When you want to keep your speakers, I recommend to go for the Lamm Hybrids or very strong tube amps.

Hi Metralla,

yes, of course. What I wrote has to be seen in this combination.
The tube amps from Lamm are outstanding with some speakers, but the
Kharma, Wilson (exception some early WP's), Magico, Soundlab, NOLA and so on
are not among them...
I think, one of my audiophile friends once had those - or similar - Kharma
speakers paired with ML2.1 because some told him, this would be a great
match. He never got happy with that Set up, he listened to a System with ML2.1
which was a much better matching and he knew he will never get it with these
speakers...
Some time ago I listened for longer time to Spectral 360 mono and I think, they
have absolutely nothing in common, Lamm units sound totally different...even
M1.2R...

The Avalon is a good Speaker, remarkable midrange, listened to it multiple
times. The sensitivity is not really a top match for tube Amps, 87dB, 3.6Ω.
The Bass has nothing to do with SS or Tube Design, I listened multiple times
with the latest Pass electronics connected and it was dead, thin,dry, analytical
and far away from a deep, full Bass or a lively midrange.
A top Performance I got from an owner with - old -Threshold amps, that was a
total different chapter.
I know owners who tried tube amps with it, but honestly, between
"great, I looooove it" and "great" is a difference. Try to
loan some from Dealers, this will give you the best impression.

I heard significant feedback about CAT Amplifiers/Avalon combo. Not about Lamm/Avalon combo

There can be several reasons for it, different design for example, different output power and so on. Lamm Tube amps shine best with Speakers which were made for this kind of Design (simple X-over, higher sensitivity) and I think you are in a good situation with your Spectral combo. It is simply a good match with that Speaker.