Best $10-15K bookshelf speaker?

Ls35a,neat, Sonus Faber, nandw silver signature s. That would be where I would start looking. 

@russbutton beat me to the punch. Pick up a pair of Dutch & Dutch 8c’s and don’t look back. Retail brand new is slightly more than 15k and you can find them used for <$10k. They are a cardiod design so you can put them within a few inches of a wall and they are active speakers so you can sell your current amp (and possibly preamp as well).  They can truly do 20Hz-20kHz without a need for a separate subwoofer. They are also Roon Ready and connect directly to your network with Ethernet cables. I’ve owned a pair for almost 2 years now and they are absolutely phenomenal. Check out their review on Erin’s audio corner.

The B&W 805 D4 Signature are spooky good speakers that bring out the midrange much more than the non signature version.  

805 D4 Signature Bookshelf Speakers | Bowers & Wilkins

if possible give a listen to the Manger Z-1

unlike any speaker discussed on this thread, in a good way 

Joseph Audio Pulsar is a wonderful speaker, and it fits your budget.