How many "general concenses" would you like? There are definite criteria for either choice ;-)
If your mains peter out at 100Hz or higher (or need to be high-passed above 100Hz to avoid distortion) then you definitely need two subs to preserve stereo directionality (which is present down to around 80 - 100 Hz) The cons are that two subs are hard to place so they integrate seamlessly with the mains/room -- the biggest issue being phase matching to the mains at any given location.
If the mains go low enough to require sub-assist only below 80 -100 (or preferably 50 - 65 Hz) then one sub is preferred. It can be placed almost anywhere, but right between the mains is preferred. If you can't do that, then place the sub at your listening position, and walk around the room noting all the spots where the bass sounds best. Use one of those spots to locate the sub ;-)
If your mains peter out at 100Hz or higher (or need to be high-passed above 100Hz to avoid distortion) then you definitely need two subs to preserve stereo directionality (which is present down to around 80 - 100 Hz) The cons are that two subs are hard to place so they integrate seamlessly with the mains/room -- the biggest issue being phase matching to the mains at any given location.
If the mains go low enough to require sub-assist only below 80 -100 (or preferably 50 - 65 Hz) then one sub is preferred. It can be placed almost anywhere, but right between the mains is preferred. If you can't do that, then place the sub at your listening position, and walk around the room noting all the spots where the bass sounds best. Use one of those spots to locate the sub ;-)