For a home cinema with BL9, I think there are some great options :
BL9 front+BL3 rear+ BL7.4 center (full ALT setup) with a beosystem 3 (the most futureproof item of B&O) and a Panasonic plasma (Beovisions 4 are extremely overpriced for what they are : a simple plasma display without B&O electronics, if you want you can buy aluminium frames to make the Pana look more B&O!)
You can make a cheaper system with BL6000 or BL4 at the rear, it will not be full ALT, but I think it's not useful to place too high quality speakers at the rear.
Personnaly, I would avoid a BV7 for its lack of connectivity, for the sound processor which is not as good as the Beosystem 3 and for its integrated DVD which will become useless as soon as you will buy a HD player. (the price of the BV7-40 without speaker is very close to that of the Beosystem 3 with a panasonic 42" Plasma panel, and there is no comparison possible technically)