Looking for a sub to put in my amps loop function

I recently picked up a Peachtree Nova 150 to drive a set of Dahlquist DQ-10 loudspeakers and would like to add a subwoofer into the amps loop function to take the load of the 80Hz and below off of the amp and DQ-10s and onto the sub. I was looking at the rythmic audio F12 but would like to know what other options are out there. Thank you for any and all responses.
Maybe I’m missing something, but is the loop on your Peachtree before or after the volume control? 

If before, then whatever component is connected in the loop won’t have its volume controlled by the Peachtree’s main volume control. If this is the case, then you’d have to independently re-adjust the volume of your subwoofer every time you adjusted the main volume control knob, and that’s just not practical. 

But maybe I’m missing something... ?  


For example, Vandersteen 2WQ insert a capacitor to the loop to create a low frequency 6dB/octave roll off, and the subwoofer connected to the speaker output and the contour is opposite of the low frequency 6dB/octave roll off induced by the capacitor.

Audiokinesis is correct.  It will not work like that with the nova.  The peachtree volume knob will not change the sub volume.  There is no way to make it work.  I have talked to David Solomon about this when he was in charge at Peachtree.  
Not possible.