Dual mono with REL Subwoofer

[devianet]

Yes, you could. Or, as you want the subs to play the mono sum, and if you want to save a socket on the back on the amps, you could just use one socket, with a phono y-adaptor branching off to both subs. You don't actually need two sockets in this scenario.

The scenario where you do actually need two sockets is the stereo-sub scenario, where each sub takes the bass of its corresponding main-speaker only and not the mono mix. In that case the configurator gives you the option to set each socket to be left or right channel, and not the mono mix of both that you'd use above.