High efficiency is critical.

You could get Khorns if you have a large enough room with two free corners. Or the Speakerlab version, to save money! Come to think of it, my Speakerlab 7's would probably work well with the Sanei 2A3 amp. They resemble a Heresy with an extra woofer on the bottom - no sub needed! Recommended!

Tekton Double Impact............ 98db efficient

For that budget range, look at speakers from Decware, Omega, and Zu Audio. If your Heresys are first gen, you could upgrade to the IIIs, then take them a bit further with outboard crossovers from ALK.

You could also go with a used pair of 604s.  I do and augment the bottom and I couldn’t be happier.