This is the first I've heard of the S2K. Looks like an interesting design using two KT88's in unison (pardon the pun). Well, if that is true about the match-up, that'd get my thumbs-up as worthy of consideration, with the caveat that Avguygeorge added - SET designs done right will certainly do vocals and strings like no other topology, but will not be as versatile as a push-pull when it comes to the wider range of applications. It doesn't bother me at all, but then I don't listen to much rock or electronic music, or other complex/demanding programming, nor do I use the SETs for home theatre. The match-up does surprise me though. Somehow I would have never thought 16watts could drive speakers with the specs of the Arros to gratifying levels. I've tried both 10 watts of push-pull and 17 watts of pentode with both 89db monitors and 90 db floor standers (both at 8 ohms). Granted, neither speaker resembled the Arros in size/shape nor drivers. Neither of those combinations really allowed me to push the speakers very hard. At modest levels (below 85db) those combinations were very nice indeed. That begs another good question - how loud do you typically like to listen?
Marco