For what its worth, I demoed S-400 and I think it is the best amp personally I have heard. Haven't heard it with stats. To me, it has almost as much bass control as Halcro monoblocks, I compared it directly to Burmester 911 and it was much more involving, although maybe slightly less detailed. If you take the best of ss and the best of tubes, it is best compromise you can make in my opinion.
Cheers!
Cheers!