I would make sure that the Revel's impedence curve is friendly with tubes before going that route. This lovely monitor is VERY carefully spectrally matched, and the last thing you want to do is to "trampoline" its freq resp with a high output impedence amp.
I'd suggest that you start with the Audio Refinement Complete ($1k new), or maybe that Levison, or other good ss output amp to get the system voiced well IN THE ROOM, and then play with tubes if that's your style. In other words start with neutrality before playing with spectral flavoring. JMHO.
