Hi SiliconTi,
As already mentioned, I would certainly not waste placing a pair of BL9s as rears in my setup. Have them as your front speakers instead. They have a lot more humfff than the BL3s and they still have the perfect precision of the ALTs when necessary. And unless you want to rumble yourself off the sofa and onto the coffee table without touching the floor, I don't think a BL2 would be necessary in my opinion.
The BV7 sounds great to me, take a wall mounted BC2 (looks so good 😐 As rears I would say a pair of BS4000s wall mounted would look and sound great.
P.S. I like the Boston store too! My BS2 hasn't returned home since.