Would you choose 1 ou 2 subwoofers for a stereo set?

First, check out hte AM Acoustics room mode simulator.  You can use it to pick ideal locations for your listening location, speakers and subs as well as evaluate where your lowest room modes will be and how to fix them.

Personally, I'd use one, on the basis of cost, foot print and performance.  I've had nearly perfect results in some situations with a single subwoofer. Having put that sub in, dealt with room modes, added appropriate EQ and bass traps I would then ask if I needed a second. 

Looks like I'd choose 2 big subs for your room, not small ones and definitely 2.

I would pass on the 10” JL. Too small, honestly I would pass on JL they are over priced and break a lot (I own two and have had 4 replacements subs…).

I agree,  definitely 2 big subs for a big room...

@tvrgeek 

That is lay intuition tv. The speed a woofer can move is indicated by the upper limit of its frequency response. Most 15" subwoofers make it easily to 500 Hz. The transient response of a sub driver has to do with the relationship of its motor power to the mass of it's moving system. One issue is certain, the distance a driver has to move is directly proportional to the amount of distortion the driver produces. The smaller driver has to move farther to produce the same volume producing more distortion. The main disadvantage of larger drivers is the size of their enclosures. I use two 12" drivers per enclosure which is like using one 15" driver. I did this for packaging reasons. I do think once you get beyond 18" the cone becomes more difficult to control and pistonic motion can be lost.