Xavier,
Did you by any chance try these with a Firstwatt Aleph J? According to some, this is a spectacular amp for the quads and cannot be damaged by any known speaker load (according to NP himself) These are single ended class A SS amps (though with some feedback) and a 2nd order distortion characteristic. Many low power SET lovers have adored this amp.
I'm collecting parts to build a couple of monoblocks -- got matched sets of FETs and JFETs and BJTs on the way, plus pc boards, and mega heat sinks. A longer term project, but something I'm very curious to hear for myself.
Hope things are well with you, my friend,
Jim
Jim Rebman -- recovering audiophile
Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).
s.e.x. 2.1 under construction. Want list: Stereomour II
All ICs homemade (speaker and power next)