Subwoofer reccomendations for B&W 805S?

I think the responses here are all good suggestions. I'm
using a Velodyne DD-10 with my Signature 805's. They work
pretty well together in my 10x12 room. For what its worth
my friend has a DD-12 which I think would be too much
for a room of my size. The DD-10 gives me all I need.

Good luck

Totally disagree, modern film is sound effects plain and simple. My HT set up is quite satisfactory for BLue Ray etc but I would never tolerate it for music. I have at least 6 pairs of speakers sitting around that are better than the ones I use for HT but I just don't bother. I use two Hsu 10" subs for HT and they are quite satisfactory. Have a pair of 12" Hsu as well besides my Nelson Reed 1204s that use 4 12" Volt drivers each , I might use them if I had a very large room. HT is trying to emulate movie theater sound, which in my experience is truly awful, worse than in the days of Altec Lansing.

so would using two 10" subs be more than good enough for my 17x15 room?

Not all subs are created equal, two good ones would be more than enough. I spent 11 months in DC some years ago, the system I took was the 805's with the 2 Hsu 10" subs, sounded quite good. I ran the 805's full range, they were intended to be used that way and used an electronic crossover to roll off the subs. One good sub will work as well, bass is non directional at low frequencies.The 805 is an exceptional speaker and it and a good sub or subs can compete in everything but sound level with very expensive speakers.