Here are some kit and
design you can use with Peerless products:
http://www.solen.ca/v1/sxxls.htm
My configuration is with one passive radiator, but I use an external amp (Rotel RB-1080) :
SUB XXLS12
Frequency response 18Hz to 40-160Hz (adjustable).
Capable of an astonishing 122dB at 25Hz.
The amp is the SUB-250R 360 watts/4 ohms, with remote control,
THD 0.08%, S/N ratio 100db.
Adjustable gain.
The crossover is a 2nd order low pass adjustable from 40Hz to 160Hz.
The subwoofer is the Peerless
308SWR51XXLS (830844).
The box volume is 1.5 cubic feet (43L) using a matching passive radiator the Peerless
308PAS425G (830548).