Given the parallel wiring, about 3ohms from 200-300hz. A stable 4ohm amplifier would be a better option. It's a fantastic design though and should still be considered IMO. Go sealed and crossed to a pair of sealed subs. I'm working on a modified sealed version of the waveguide TMM that's almost complete of the finishing stage. Listening impressions are amazing. With all the great deals on AVRs these days, sounds like a perfect time for an upgrade considering the savings of building the BAMTM!