I can understand why your friend believes that 30 watts is not getting full potential from the MLs.
However it is doubtful that a 100 WPC tube amp will fare much better- they just don’t have the reserve power that a smooth solid state amp would have and usually are rated at lower power with decreased impedance loads.
I suggest a solid state amp that can "double down" as the speaker load is reduced. With panel speakers I have heard excellent systems driven by the higher wattage Tube D topology of the Rogue Audio DragoN amplifier-
Another contender is a used smooth sounding Mac amp, this one would do the job nicely.
https://www.usaudiomart.com/details/650271441-mcintosh-mc302/

