Hi Jody:
The IWS88 is rated at 4-ohms so you limited to driving just one IWS88 with our dedicated Subwoofer Amplifier, most of which are 4-ohm rated as well. The minimum Sub amplifer for this speaker would be our SMP200 rated at 200 watts RMS at 4-ohms with peaks at 400 watts. If you want to add a second IWS88 you will need a second sub amp as well. Both the SMP300 or SAM300 will work as well.
TIML/11-8-2021