Tube Amps Watts vs SS amp

It's most likely been already covered but a watt is a watt whether it is sand or glass. All other factors will influence how amps work in their installations but a Watt is the same no matter where it comes from.

It is the clipping that is important. Glass clips softly, sand hard.

May want to consider a solid state amplifier with a little more ‘meat on the bones’ to emulate (75% or so) tube sound but maintain the high damping factor and needed power. Consider used GamuT D200 or possibly older Clayton Audio amplifier. Both amps are built to last.

As others have said, tube amps provide a more usable power band than most solid state amps.  I've been in audio for over 40 years, and have listened to countless amps, and of this I have no doubt.  Another point on most tube amps is that the output transformers allow these amps to deal with complex loads quite well.  Sonically, I have always found tube amps to be less fatiguing in the mids and highs.  

That said, the tradeoff is the low end.  AR9s, even with a massive tube amp, will be soft in the bottom end.  This is the biggest tradeoff in my view.  That, and the dynamic compression that occurs at higher volume on tube amps, will lead to a choice.  If recreating the energy of a concert, with gut punching bass is what you're looking for, best in class solid state is hard to beat.  

Roberjerman, I went back and looked at the Heresy's timeline. It does date back to 1957 but it was called the H 700. It was given the Heresy name with an update in 1972 which was probably the year I got them as they were marketed at the time as new speakers. The K horn is the longest running production speaker of all time! I remember listen to them at the store I eventually got the Heresys at. They were being powered by Marantz Model 9 mono amplifiers and a Model 7C preamp. The turntable was a Thorens TD 124 with an SME arm. I don't remember the cartridge. That was the absolute State of the Art at the time. It had no problem doing realistic volume levels.