Hi Paul - I agree that's a very nice, highly resolving system you've put together, and i also agree that some tube magic would do you good. The FS is a perfect match, IMHO, mostly becuase it's very neutral and honest - does all those audiophile things (soundstage, imaging, dynamics, etc) very well - but more important, it gives an emotional connection to music that's I've never heard with any SS preamp. There are plenty of "musical" tubed preamps, and plenty that exceed in transparency, soundstage etc - but the FS exceeds in BOTH.
I received the US made 1959 Amperex 'Pinched Waist' 6922's today, and Im still letting them settle in, but right off the bat, they're truly amazing! Exceptionally quiet and neutral. Notes are very fleshed out. its pretty amazing. More on that later, as they settle in. Suffice it to say they are my new (final) reference, though im keeping the cryo'd 1959 6DJ8 Miniwatts (aka Bugle Boys). I sold the white letter d-getter 6922's no another FS owner, btw.
Anyway, Paul, we're all glad to chip in our persectives (no matter how biased) - so let us know how your journey develops!