Hopefully others can respond with experience on the Focal Spirit Classics. Have
never had the pleasure of hearing them.
Another idea, is to talk to your cube mates and ask them if they think they'll be
bothered by fairly low level music leaking from your headphones. My experience
was in a cube cluster of 4, the low level sound from open was very distracting to the one
guy sitting right next to me. The other two weren't bothered. I went back to closed
to be able to do the volume I wanted. But it may also depend on how quiet or noisy
your environment is. My office at that time was almost like a library.