Full range speaker recommendation

A second vote for Klipschorns for your tastes in music. I found mine shone on classical and big orchestral works in particular. Pure Audio Project Trios are also amazing. 😎 BH 

+1 Focal. Used Kanta 2 perhaps. Good luck! 

Salk are my next venture!

Sonus Faber Lumina Vs should work well in that space.

If you want to keep a form factor similar to the ATCs, Spendor Classic 2/3s will be fuller sounding than the ATC's.

Lastly, as a total alternative, it's worth giving consideration to Magnepan (Magneplanars) - they might lack a bit of punch on classic rock but they are superb speakers.

Recently added a pair of Focal Aria 936 and am quite smitten. If possible to audition somewhere, may be worth a listen.