all I can say at the moment, that both amps are true to the music. Speaking of the Atmas, the amps give you a sort of middle of the hall placement with most classical recordings and a midrange which is impeccable, adding nothing, taking nothing away. However, if things get really loud, they do clip on the Sound Labs. The VTL's with their 600 pentode watts don't, they move you closer to the stage, are more powerful in the lower bass regions, something you don't miss though with the Atmas, because their blend between mid , highs and lows is almost perfect. Listening to the VTLs is like changing your seat more to the front, closer to the music, which is represented most realistically. I still have to find something to fault them. But getting that close, also in a real concert can have its drawbacks, you tend to concentrate on details, instead of taking in the entire "gestalt" of the music, which the Atmas achieve beautifully.
In listening to jazz-combos, the VTL throws the happening right into your room, with absolutely uncanny realism and rocks teady players in excellent three dimenionality. The Atmas are a tad more polite, also again here a little more laid back, but in their way just as musically convincing.
Both amps are excellent achievements I would say, at least to my ears.