Hi Larskoelle
First of all, there seems to be a general aggrement in here that you should not mix ALT speakers with Non ALT speakers. However the prefference is ofcause individual. I myself have BL5´s as front and BL3´s as rear speakers and find it to be a very nice combination for surround sound. Remeber that rear speakers are not used that much in a surround setup so the most important decision is what to place in front of you. Also when you write wether you should get Bl5´s i trust that money is not an issue here. With your current setup, the easy soultion would be to get BL3´s as you already have a sub. You could also consider Bl9´s or go for the best, Bl5´s. With BL9´s i dont think your BL11 will do any good anymore, and if you choose BL5´s I am certain i will not longer be needed.
One thing you also might want to consider if you are looking into having surround is that the BV10 is not the ideal choice. Yes is has the surroundprocessor and everything, but the speaker in BV 10 does not compare to say a BL7-4 under a BV 7 or BV 4 in a surround setup. Ofcause BV 10 will work and everything, i am just letting you know that it is far more ment to be a standalone tv.
So if you want the best, get BL5´s and sell your BL11, if you want greatness, get Bl9´s and maybe sell your BL11 and if you want a very nice setup and prefer the smaller and stylish speakers, get an aditional pair of 3´s and keep your sub. My advise is not to buy BL8002 or 6002 or anything else than the three mentioned above as they will not have the ALT and probably not sound that nice in combination with your current speaker setup.
Good luck with your choice.
/Ehlerz
BV7-40 MK IV, BL5´s, BL3´s, BL 3500, BL7-4, BS3000, BC 6-23, BV 1, BS3.