Is Bass Non-Directional In A Two-Channel Rig?

You can, but the timeing would come into consideration.
Give it a try and if you like it, go with it.

Sub bass should not be directional. You should not hear where it is coming from when set up properly. It may take a while to get it right so be patient.

When I first got my subwoofer I had it sitting directly behind my side of the couch via wireless connection. A friend of mine came over to hear the subwoofer and assumed that he was hearing the "before" since he didn't see the subwoofer. He was, however, wondering why I need a subwoofer based on what he was hearing. It's now next to the right channel speaker because the wireless connection didn't play well with my wireless printer or internet connection.

I believe that they have done studies showing that people can't pinpoint a direction below 80 Hz.

It should be non-directional but the timing issues remain, anyway, especially with wireless connections that introduce 10-20msec or more of delay. This can work but putting the sub up front with a wired connection makes it a lot easier.

Kal

Dual stereo L/R time aligned subs matched up with the mains is the way to fly. Even if you cross over the subs at 40hz the actual cabinet enclosure acts as a giant passive radiator creating at least 4th order harmonics that need to be blended in to the mains. It is very easy to hear the placement of one and near impossible to hear the two as described. Each woofer will greatly benefit in speed and transparency if the cabinet is direct coupled { use brass] to the mass of the floor. Direct coupling {use brass] the woofer cabinet to the floor will limit the upper harmonics into the midbass and beyond resulting in much more clear mids in the main speaker pair. Tom