External Speaker Volume Control

Yes, I've searched, and not finding much.

I'm driving a set of LaScalas and Heresy speakers from one amp.    (Yea, sounds pretty darn good)

But of course the LaScalas tend to drown out the smaller Heresy speakers 

So, I would like to even out the sound.    

I am considering adding a second amp, but wanted to see if anyone know of an external volume control I could put in line with the LaScalas to pull down their sound level a bit without sacrificing quality.

Any thoughts?