Class A Watts

I tend to agree, Watts are Watts, though I find Class A is the only way for me to listen to SS amps, but that's just me.

Where there does seem a difference is tube and SS watts. The former seems to handle comparitively difficult loads, beter than SS amps with the same rated output, given sufficiently robust output transformers. Whether that is only because of the well known "Benign Clipping", that charecterises tube amps, I am not sure.

My earlier XA100.5 monoblock's from Pass were superior in drive and dynamics compared to my modified Nu-Vista 300 poweramp from Musical fidelity which gave more than 2 times 350 watt by 8 ohm.

I own a Sugden A21SE and at only 30 wpc Class A it does not play louder than other well designed 30 wpc gear, but it is definitely quicker and approaches that oft elusive tube sound. The characteristics of speed, solid bass response and openness of vocals.

If your speakers are low impedance, or have an impedance curve that varies quite a bit, both current delivery and output impedance of the amp (damping factor)will have a greater effect on the sound than the amount of watts that the amp puts out.

However, there are A/B amps with no switching distortion and much quicker than lots of class A amps. Just because it's class A doesn't mean it's better than any other topology. Conceptually, it is ideal with regards to this issue. As far as tubes go, you're not going to get there without mosfets in an ss amp.