One 12" sub, or two 8"?

Pretty much what the title says! I'm upgrading my gear, and have a Denon X1600h arriving next week. This is the first time I have the option to run multiple subs.

Am I better to run one 12" Subwoofer, or two 8" ones? I'm tight on space, so don't have the option to run 2 bigger subs. Both corners are around 4 feet from our listening position. Currently looking at the DaytonAudio 1200 12", hoping to get it for $120 open-box or on sale.

We often have the bass lower than optimal so we don't wake up the kids..!

Room size is 11ft by 15ft, with an "open plan" 6ft archway to our kitchen on the left of the listening area.