The easiest route here, of course, is to keep the Beocenter for your stereo fronts and use a different amplifier and speakers for your surrounds and center. If you've got decent speakers, there's little need for a subwoofer.
That's the plan I have for my Beosystem 2000 as well, obviously, it doesn't support surround sound output and has a limited number of inputs, so I'll be looking for a separate stereo amplifier for my surround (and, if neccessary, center) speakers. I have a pair of beefy Magnat columns for my fronts, which provide enough grunt in the low end to stay away from a spare coffee table, er... subwoofer.
You can connect your BC9500 to the television's audio output (on the SCART connector) to get stereo audio from any source connected to the TV. The AV7000 or 9000 is a nice option, but you're going to need to be creative with your placement. Possibly the -9000 with the BC9500 and your HD video sources on top?