REL R-Series vs. B Series

Not asking for non-REL alternatives. What I am asking is how much difference I would see between these. Plan A is to have a REL R-505 with the fronts (B&W 802Ds). THen to have one REL R-205 each with the center (B&W HTM4S) and surrounds (B&W DS8s). Power to speakers from Rotel 1095. Question is how much better B series is or if I have enough bass. Room is about 15 x 17 with 11 1/2 foot ceiling. Thanks
I can't speak to which series is better for your application, although I would say the B series is a better quality sub, and better suited for pure audio appications, and the R series is better suited for home theater.

However, if I understand your plan A correctly, your 15' x 17' room will have a total of 3 subwoofers? If that is correct, I think that's big-time overkill. Two high quality subwoofers in that room will be fine for home theater. I'd focus on the quality of the sub(s) you purchase... not quantity of subwoofers. More is not always better.
I own a B3 and compared it to the I think it was the q405. The B series is ported verses the Q series which is a closed box. They sounded very similar until you hit the lowest of notes and thats where the B3 came though better. The dealer had a song called skates that had some very very low notes on and yes the b3 did 'break up' in 2 parts of the passage but the other closed sub broke up 5 different places in the passage. I didnt compare it to the B1 but my dealer said the B1 would have handled it. I didnt have the cash for the B1 (actually I pushed my spending limit a couple of hundred over but not the 1000 difference).

My room is 22 X 12 with uneven ceilings too. I've read where bass notes are non-directional so you can put the sub anywhere but that is not totally true. I really wish I had 2 subs (maybe someday) but 3 for your room I would say is severe overkill. 2 in the front sound be great for your speakers. My speakers are Cyrus 782 monitors with a freq resp of 70 - 20khz +/- 1.5 db -6bd at 50hz so I really needed a sub. The REL does blend in very well when set up properly. It took me about 6 months to get it just right for my room. One thing I did fight for about 2 1/2 moths was cable length. The REL came with a 35' cable and my speaker cables are 10'. I cur the REL cable in half thinking it was only 30' but it still was not quite right. Then when I cut it to 10' everything sounded fantastic.

So like Pdreher mentioned the R series is more of a home theater sub where the B series is more musical. Personally I think the B series is better and should work as well in a HT setup. That way if you just want to listen to just music I think you would be happier. Most people when watching a movie are paying a lot more attention to the movie than the audio portion.

Last the B&W 802D's are great speakers and you may really may not even need a sub (unless you need the walls to shake). I would see if you could demo 1 B1 just to see if you can justify the cost of the sub(s). I would place the demo as close to the center speaker as possible as where mine is to the left of the left channel and I can hear slightly more bass from the left. I have no room in the center of the listening area but for me I think that would be more ideal and less expensive than 2 subs because bass is somewhat (not totally) omni directional.