As good as I’ve heard from any solid-state DAP.
My SP1000M comments are here (which is fundamentally the same as the SP1000, just smaller and without the materials options) and SP2000 are here.
I do have a love for the N8’s tube output, but it’s definitely colored vs. the A&K units. And the A&K’s are the quietest (i.e. lack of noise/hiss) units with fussy/sensitive IEMs I’ve ever heard.