Why do you need so much power?

Complicated. Much depends on particular match, I guess. 500 seems excessive but 25 seems bare minimum. And what about current?

@mulveling, thanks for the response.  I listen almost exclusively to classical, opera and jazz; not so much orchestral recordings (so a lot of piano, violin, vocals).  What's most important to me is clarity, detail, transparency and imaging. 

The reason I'm partial to the First Watt is that those amps are designed to be musical--an ethereal and subjective characteristic but nonetheless, important.  I'm a violinist, so I value a system that communicates what the musician intended.

Let's see.  I'll try out the J2s and see what happens.  

Just get a sugden a21se, its class A and a good match to your Tammy's. 30 watts, all you will need. Mine is seldom turned past 10 am on the volume, plenty loud.

I used a Bedini 25/25 with the Quad 57's for years. Perfectly satisfying! But that speaker is severely limited by power handling and easily damaged.

2 watts, 20, 35 watts, etc etc. 

  there is no substitute for headroom, and having the reserves for those crescendos’ / peaks / quiet passages......and the full on massive orchestral frenzy of woodwinds, bass, as the fury of the full orchestra slams you like a ton of bricks,......... you will need the watts, to make the smooth transaction from the small flute, or simple cello, to the full orchestra smash which happens awesomely in classical music.
  Not having the reserve and power to deliver these peaks will result in unhappiness. 
 Speaking from experience. 
https://www.youtube.com/watch?v=Sg14jNbBb-8