Several different 50-60 watt tube amps run with different speakers produced bass at least as good as 150-200 watt solid state amps.
Sorry but BS alert.
A watt is a watt unless the specs are juiced differently.
Soft clipping makes X # watts seem to go further because peaks get clipped in a listenable manner. But 50-60 watts is equivalent to only 50-60 watts period no matter how produced. It may sound fine subjectively but it is NOT, repeat NOT, the same as 150-200 in terms of dynamic peaks possible without distortion.
If you have a good combo of amp/speakers, more power may be overkill at some point unless you have need for even louder potentially ear damaging dynamic peaks, but that is a different story.....just two different ways to effectively slay the beast.