MMG sub hookup....

preamp to via rca subwoofer, then rca from sub output (crossed over) into your amp.

@batman So....the rca s currently from preamp to amp that is in now....   

Run from from pre to in of sub
And out from sub with rca s to amp input.

Because amp of course has only one pre in left and right..

Confirm?
Thx...

@batman
My sub only has line ins

And speaker input
And speaker output.

@batmanI could split pre and run to sub..
And a run to amp then...

If you want to high pass to the speakers you can use this HSU high pass filter. If you want to run the speakers full range you will need Y adapters from preamp into amp and into the subwoofer!
I use this to high pass to main speakers!
You will need 2 pairs of Y adapters to do any of these choices!

http://www.hsuresearch.com/products/high-pass-filter.html