I have an X350.5 and both an Audio Research Ref 2 and a Pass Labs X-0 preamp that I use to drive the amp which mates with a pair of Avalon Ascents and a REL Stadium 3. For most music I prefer the Pass Labs over the Audio Research. Violins seem to have a better decay effect with the tube preamp, but female focals are clearly more musical with the solid state combination. I have owned many tube amps and I wouldn't trade any of them for the X-350.5.
Happy listening.
Jeff
Happy listening.
Jeff