While two subs are definitely better than one, the idea of a separate left and right channel sub isn't really necessary because bass under the crossover frequency that will get played on the sub is non-directional. That is to say, you can't tell where in the room it's coming from anyways. This is why on multi-channel recordings, the LFE (Low Frequency) channel is always one single channel. There is no need to have it broken down further.

With great power comes Awesome irresponsibility.