With the budget you are working with, I believe what you are looking at will be sufficient. I think that with those surrounds you will be going beyond your budget? If your willing to stretch some, then by all means go for it
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. Otherwise, getting a second pair of B-20s for the rears will do the job also IMO
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P.S. I advised dual subs b/c the AVR you listed has dual sub outs, and having ran dual subs before, I achieved great success I must say. It takes some time, but it'll pay off in the end..bass everywhere
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. Why look at a 15" sub if I may ask? Was it for extension or impact? If it's for impact, then given your room size you can even go dual 10" subs
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...just a thought.