Atma-Sphere is supurb equipment -- well worth a listen.
Perhaps you already know this -- in buying a tube preamp to mate with a solid-state amp, it is important to make sure that the output impedence of the preamp and input impedence of the amp are appropriate for each other. The output impedence of some tube preamps can be quite high in the bass (e.g., BAT -- 3 kOhms), while the input impedence of some solid-state amps (vintage Rowland, professional gear) can be as low as 600 Ohms. As a (very) general rule, the input impedence of the amp should be at least ten times the output impedence of the preamp at all frequencies.