I am out of my depth with the AV9000 but with my set up the products come with a pre-amplifier built in which controls volume, bass treble etc. Therefore use the Beo4 or whatever remote you are using. All the Detoma does is the power amp business. Which is great as you just need the Beo4!
You'll need to check your AV9000 has a pre-amp module. I'm pretty sure it would have - needs confirmation from other experts.
You won't be disappointed with the Detoma if you go for it - it is SO much better than the MCL 2P I tried for a bit which looked like a brick (well it was supposed to be hidden..!!) and popped massively whenever the system powered up. The Detoma was built for yours and mine scenario in mind i.e. love B & O system but not too keen in the lower end speakers. I'd love to see the BL8000 redeveloped with some cunning bass reproduction and ALT for the treble. Anyway, hope you find out about the AV9000.
Regards
Jonathan