"60 tube watts can't be greater or equal to 100 SS watts it can only be less."
yes, but soft clipping nature of tube amps in general compared to SS may allow things to go louder off the same # watts than SS and still sound good.
Some Class Ds might have favorable audible clipping characteristics as well, but Class D generally enables you to throw power at teh problem more efficiently than otehr SS amp technologies so clipping may be less of an issue in general with CLass D than SS in general as a result.
Clipping is always something better off avoided or minimized to the max extent possible in that it will always have a major negative effect on the sound when in play, but not to the same extent with tube amps as with SS in general.
Highly efficient Class D technology can serve as a good insurance policy against clipping compared to many SS amps of comparable cost. That alone is a good reason for me to invest in a good Class D amp and never look back.
Clipping will be less of an issue with more efficient speakers also. Tube amps are accordingly at their best here with high efficiency speakers designed to work well with tube amplification.