I would place it on the piano. You run the risk of the tubes picking up the vibrations from the speakers and feeding back when on the speaker (microphony). Some amps are more susceptible to this than others.
I have used my Decware mini torii 4 wpc with my Klipsch Quartets and they rock, almost too loud at times. The decware is very well built. Not flashy finish but not cheap. I also used a Grommes PHI-26 2/6 watt with the Klipsch and sounded great.
Decware as I mentioned, and others on this thread, is excellent sounding gear. It may look utilitarian but far from cheap. If great sound, synergy with your speakers, pickup the phone and speak with builder/designer, and lifetime warranty - may not be your cup of ☕️