Lowthers and subwoofers?

You are defeating the purpose of "purity".
Having a sub will either require a crossover or some overlap of frequency. I refuse on principal...

I use a Sunfire sub with my Lowther Medallions. I run the Lowthers full range and set the subs for 60hz crossover. If you do not use subs you will not get much base below 50 to 60 hz. I don't feel there is any compromize at all. The Lowthers are handling with the single driver from 60 all the way up.

Do you want Principal or bass...
No disrespect meant to Elevick, but I'd take bass. The sub having its own amp, takes away ruining your full range driver. Of course, careful set up with room placement, crossover frequency, maybe a phasing dial, but in the end, I would take the subwoofer, no question for me... I hope I still have principals.

I had heard, maybe a dozen times, a pair of Beauhorns with RELs and the RELs just seemed slower, you could easily hear them. Just from these experiences my choice would never be a REL but with that being said I'm sure there are other subs that could be better integrated.