One or two subs

For your application, the single sub might be better.

Since much of the low frequency signal is essentially mono in nature, the output of two subs will likely cancel at certain frequencies unless they are fairly close together.

A 50 Hz sound wave would be a bit less than 23 feet long, assuming the speed of sound is 1125 feet/second at sea level.

A half wave would be 11 to 12 feet long. If your subs are 11 to 12 feet apart, the peak pressure from one sub would reach the other sub as it is making its low pressure point, cancelling its effect at that location, assuming a mono signal.

If you are at some arbitrary listening position in the room, the sound wave cancellation would depend on the frequency and your distance from each sub. For a mono signal, the best positions would be equidistant from the two subs.

Off the center line, there will be frequencies where the two subs will have an additive effect, resulting in a fairly uneven frequency distribution.

Room resonances further complicate the situation.

Marty is right that room resonances will be largely determined by the room dimensions, regardless of the number of subs. Careful placement of the sub or subs can help a bit, but the walls will still be the most important factors. (Like, it's very hard to reproduce a sound with a 30 foot wave in a 26 foot room, no matter where the sub is or even if there are multiple subs. On the other hand, the room will tend to emphasize sounds with 26 and 52 foot waves.)

Using multiple subs to try to reduce the impact of room resonances is difficult and not very effective, especially since the output of the subs will be reinforcing or cancelling at different frequencies as a function of how far apart they are and where they are relative to the listening position, as well as dealing with room resonance factors.