Thanks. I confess I have never heard Quad electrostatics with Naim but they do have their fans here.
I was an LS3/5a owner for years (of which, you may know, Spendor was a licenced builder) so your experience of Spendor, and mine in hi-fi retail in the early 90s where we sold ESL 63s (very often to people who loved Spendor LS3/5as) made me think that ESLs might be the answer. Plus, I don't think they would have the sort of rumbley bass to bother fellow appartment dwellers.
I don't know how widely available the latest incarnation are in the US.
Enjoy your music.