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

I use two but I have used a distributed bass array of four placed asymmetrically within the room which eliminated all the rooms standing wave bass modes and provided immediate sense of timing or room loading.

I've since manage a similar but not as total effect with two bass mode carefully positioned subs.

JL Audio makes a potent high quality product. Personally I found their F113 automatic / frequency only optimization lacking the flexibility of added  manual adjustability. This Youtube shows the Quality.

https://www.youtube.com/watch?v=GQ10cQ9O2L8

FYI, since REL are -6dB "Sub-Bass Systems" their frequency rolloff begins so early they usually don't excite a rooms standing wave bass modes allowing for greater flexibility of positioning at the cost of actual subwoofer extra low frequency presentation. Claims of superior musicality are purely subjective.  

definitely a pair

TWO subs for sure….2 subs are sonically better than one, even huge one. I don’t think 2 10” subs will properly pressurize your space. Unless you’re only listening to acoustical jazz you will sense something is missing. I have multiple SBS subs that do a great job in my HT room but for two channel listening I would go in that direction. Get two subs to compliment your lovely B&Ws. JL or REL should be you’re candidates. 10” subs will be lacking in your large

space. First choice for me would be two JL F112 V2s. They are very fast and the built in DSP room correction is fantastic and a relatively small footprint. +WAF. THE RELa are great but have less power and don’t hit the same. Good luck and cheers 

Two subs. Try one in the front and one in the back to see if it makes a more 3 dimensional sound. 

Always two or more sub woofers. 
 

I have two REL S812s and love the balanced distribution and performance. Tuneful and dynamic.