Not much will handle a 1.5 ohm load - I'd suggest contacting the Outlaw warranty people before trying it.

I assume that your subwoofer has 2 voice coils of 3 ohms each, and you are considering wiring them in parallel to get the 1.5 ohm load.

If you can get at the wiring in your subwoofer, the alternative is to wire the coils in series, producing an easy to deal with 6 ohm load.

(+) wire from the amp goes to the (+) terminal on coil 1, (-) wire from coil 1 goes to (+) wire on coil 2, (-) wire from coil 2 goes to (-) on the amp.

I did this to wire a pair of 4 ohm bookshelf speakers together as a center and it's working fine.