kinda, kinda not. but honestly, i don't know if such claims are really true or not. when SS amps runs out of juice, the resulting distortion is quite audible, it (the clipping) will sound like a badly tuned radio. while for tube amps, when it runs out of juice, the distortion sounds less "ugly". none-the-less, trained ears can hear when a tube does run out of juice. so in reality, they both run out, but tube does in a more graceful manner, giving the false impression that it is more powerful. there might be other factors too. most SS amps are those little class B amps with an inadequate power supply reservoir which drains more quickly when there is a long duration of loud passages. while most tube amps have a more generous store in their power supply and can sustain loud passages longer. i stress the word "most". the top quality SS amps have very very adequate power supply, while the poor quality tube amps don't. but overall, it may give the impression that tubes are more powerful.