Are Pass Labs amps probably the best ever you can buy ?

I liked the recent interview with Nelson Pass in Stereophile (I think it was Stereophile)...his constant experimentation with his gear and sharing designs with the DIY/Burning Amp crowd is cool. He built a gizmo to add in "even harmonic distortion" to an amplifier (He gave some of these things away at a "Burning" gathering) as part of a theory that that he feels makes music sound more musical...or something...all validating the mysteries behind my single ended tube amp sounding better than any SS amp I've heard. Pass is the rare open book designer who writes his own manuals and shares pretty much everything he does and is funny and seemingly less of an egomaniac than many great designers out there.

It's not really a thing designed to add second order harmonic. It's a pot that balances the VAS. When the VAS is out of balance one way or the other it produces negative or positive phase second harmonic distortion. P3 in the F5 does the exact same thing, except with the F5 you're putting DC on the outputs when you turn it so you need to adjust it along with P1 and P2. 

That kind of adjustment makes a big difference. After having experimented with it quite a bit, I think Pass is dead right on his theories about distortion. If you want deep, enveloping, layered imaging, you want some negative phase 2nd order distortion. 

What about First Sound pre for Pass Lab