Todd was nice enough to shoot out the switching power supply so I was able to do some quick testing. Due to work and classes I spent less time here than earlier. HD800 used for everything.
Is there a difference between the power supplies on the Arete and Peak? Yep. Not so much punch (at least with the previously mentioned albums) as atmosphere/space shaping with the Volcano - a (at least perceived) resolution enhance. It was so in both cases, though slightly more apparent on the Arete as I expect the tube on the Peak was performing some of the same 'atmosphere' duties.
In fact, a tube change on the Peak is how you should probably think of the scale of changes on both. Obvious? Yes. Essential? Not at all. Would you spend an additional $700 for a better tube? In this range I expect many will upgrade, but my fear is that goal will prevent others from considering the base. Both stocks still clear the transparency test against the P-1u for instance. As I no longer have a GS-1 to compare, I'm not going to declare a winner, but my suspicion is the Peak or Arete with stock PS would at the very least compete extremely well.
I could easily live with either Arete or Peak and the stock PS. And stock or Volcano I'm still confused which amp I prefer.