The effects or contribution of a sub in a large space will be relatively small. Setup and sitting arrangement are crucial in this circumstance. Listening distance from speakers preferably not more than 8' or you would lose the scale, enveloping sound and bass slam from the 805S ie. the whack of drums and the surreal feel of live dynamic music. A larger full-range floorstander will perform better but the 805S can sound decent if listening in near to mid-field arrangement.
Is a 23x16 room too big for B&W 805S bookshelfs?
I will have a dedicated room in our new house, and it is 23x16. I'm coming from a 16.5 x 15 room, which I thought was just fine for them. I do have a sub and active crossover which sends everything 80hz and below to the sub. Also the room will be fully acoustically treated.