Quick update-this evening for the 1st time I rolled a pair of NOS Ken Rad black glass 2A3's in for the Sophia Princess tubes. I'm not ready to declare a preference yet, but certainly the Stratus lets me easily hear the difference--and so far I'm really digging the Ken Rads. I thought the Princess had a great 'creamy' mid, but these KR's may have it over them. The KR's are a bit more laid back, with less 'shimmer' (for lack of a better term) on brass, etc., but female vocals with the KR's are so sweet and right up my alley!
I can't even imagine what a pair of single plate NOS 2A3's would sound like, as everything I read indicates they are sublime; maybe my pocketbook doesn't want me to find out!