Is it better to have two matched subs or one

I've read that additional subs help with the bass "in the room" but don't most people sit in one spot? And if that spot has sufficient bass from one sub, what do additional subs add? 

Regarding "stereo" bass, what MC says about the signal below 80hz makes sense, but what if the recording mix has different amounts of signal in L & R? Then, having just one might not be getting what's supposed to be coming through the other, right? Or maybe that's just a red herring, and songs are never mixed so asymmetrically. 

Hello,
Imagine your house with a stereo system in the family room to play music. You have to turn it up in the family room to hear it a little in the bedroom. It’s loud in the family room and normal in the bedroom. If you had speakers in the bedroom too connected to the same music then both rooms can be at the same loudness or normal volume. Using more than one sub does the same thing. You are blending the bass in the room which is easier with two because both can be at normal volume instead of one having to be turned up louder. Plus, The room plays havoc on bass. It’s the hardest thing to control in a system. I also have a separate theater subs for surround sound and use 2 REL subs for music. If you know someone with a sub you can borrow from try it out. You will be very happy. Then you can pull the trigger and buy the second sub. 

@hshfi Thanks. That makes sense. I have a second sub with my HT system of a different make that I can try. It's a Klipsch while my main sub is a REL. Different calibers. I will try two subs with those and see what happens.

Matched means very little with subs. Room placement is more important to low frequency distribution.

I was misinformed by REL who said their high level subs should be identical.