Who to trust when buying vintage ss ?

@tonydennison No. AB.  Pure Class A runs HOT. You don't need or want that. Especially at this low price point. 

Are these Class A?

@tonydennison Without getting into the nitty-gritty, you need twice the power to get a 3dB increase in perceived sound volume. The corollary is that at 30w, you'd take a -3dB hit. To get twice as loud (+10dB), you need ten times the power. Anyhow, unless he's blasting it, it's 30watts of clean power versus 60 watts of grainy old components grinding away through old potentiometers and dusty caps. 

The PM6007 is 60 W and the Rega is, I think, 30 W. The speakers would have to be real, real, real sensitive.

Avoid receivers. Something like the Marantz PM6007 or Rega Io.