The Lamm's use extremely expensive output transformers and have excellent power supplies, the result being that their wattage rating is largely meaningless and they can control speakers that ostensibly much more powerful tube amps cannot. I still doubt, however, that they are as quick as they need to be to accurately reproduce upright double bass on a speaker with an impedence that drops below 3 Ohms in the bass.
As for Air Tight, I think it is superb equipment, but a $10k tube amp made by a builder having Japanese labor costs is not going to have output transformers of the quality needed to control a speaker that drops below 3 ohms in the bass (output transformers are by far the biggest single cost in building a good tube amp, and really good transformers are really expensive). The $50k Air Tight Reference, however, is another story, as are Audio Valve's big Challenger monoblocks, the CAT amps and VAC's best amps. I can suggest the VAC 70/70, as it can drive low impedences (it is totally dual mono, all the way down to two separate power cords), is very transparent and can be had for $5k-$6k used, but there will still be some tubbiness to the bass.
Have you considered the darTZeel?
As for Air Tight, I think it is superb equipment, but a $10k tube amp made by a builder having Japanese labor costs is not going to have output transformers of the quality needed to control a speaker that drops below 3 ohms in the bass (output transformers are by far the biggest single cost in building a good tube amp, and really good transformers are really expensive). The $50k Air Tight Reference, however, is another story, as are Audio Valve's big Challenger monoblocks, the CAT amps and VAC's best amps. I can suggest the VAC 70/70, as it can drive low impedences (it is totally dual mono, all the way down to two separate power cords), is very transparent and can be had for $5k-$6k used, but there will still be some tubbiness to the bass.
Have you considered the darTZeel?