will angled subs cause cancellation?

what is the reason for having them face each other? space, looks? what kind of vehicle are you putting them into?

Not exactly the best idea. This will work if the box is ported only, otherwise you will only have output from one sub at a time, the other sub will yes be out of phase and cannot get it's wave into the cabin. The Rockford He2 is a pretty good sub but generally prefers a sealed enclosure. Any properly constructed enclosure built to the appropriate airspace for the sub and the vehicle will play loud and clean. True that a ported box can sometimes play louder, but in most cases a sealed box yields way better results, a moderate angle towards each other is perfectly acceptable, I imagine this was what you were asking.