Vandersteen 1C to 3A Signature

I currently own the 1Cs, paired with a Naim Nait 5i. I like the sound, have had these speakers for the better part of 15 years and I still love their presentation, the openness and sense of space they provide. They are fabulous to my ears.

Which isn’t to say they are perfect, they don’t like being played too loud (seem fragile, break up at higher volumes), and the bass isn’t as deep or (more importantly) as defined as it could be. Also I sometimes hear some lack of refinement in the tweeter (although at other times it sounds positively glorious, especially with horns and flutes).  So after refinishing the basement and adding a big TV with prewired surround sound I found a used Vandersteen center speaker, so I’m thinking of moving the 1C to the basement and getting a different (hopefully better) speaker for upstairs. I did a bit of research and it appears Spendor is supposed to be a good match for Naim, so I was able to borrow a pair of S8E to try out. You can tell the speaker can handle much more power and can play cleanly at those high levels, and the sound is nicely balanced throughout the frequency range, but they sound like boxes. The Vandy’s don’t. I think I’ve written off Spendor, Proac, Totem and the like, as the design looks similar.

I should probably stick with Vandersteen or similar sounding speakers. I have an opportunity to buy some 3A Signatures, but am afraid I will lose the lithe nature of the 1’s which I like, so I’m looking for opinions on this, and maybe for suggestions of other models that would sort of fit into the sound I’ve tried to describe. Thanks