High efficiency is critical.

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. 

Try to find actual test results for sensitivity.  The two Tekton speakers reviewed by Stereophile found that the actual sensitivity of the speakers was abut 6db (!) lower than advertised.   

Altec Valencia's or Alec 19's! I have owned the first and listened to the 19's.

Try to find actual test results for sensitivity. The two Tekton speakers reviewed by Stereophile found that the actual sensitivity of the speakers was abut 6db (!) lower than advertised.

This is not just a failure of Tekton, overrating sensitivity figures is a routine component of specmanship.

However, 92 - 98 dB is merely "high efficiency" for non-horn loaded speakers. :) I think the original poster is looking for 100+, which is strictly in the realm of horn and pro audio.  If you are trying to use ultra-low power (~ 5 W) amps then you have to have this above all.

Best,
E