Edit: The 600D is a class D mono amp.
www.directed.com says it's one ohm stable. This may help you out:
One ohm wiring Assuming the subs are DVC, you can wire the subs parallel(see pic- 4 coils, 1 ohm load) to get a one ohm load. If you already have it wired this way, congrats! You are getting the most power from your amp.
