Hi Minh...when you connect your AV7000 thru the converter (data link to ML) to the BS 9000..... you AV 7000 becomes the master....all speakers are connected to the AV...not to the BS 9000
On the back of the AV there are Powerlink outs for front left and right AND rear left and right....just take the powerlinks on the one of the rear powerlinks...(powerlinks have both R and L in each)....plug in a simple RCA converter...and run to your amp...then on to your passive rear speakers..
The audio at the REAR powerlink will have the delay when you set your AV to the prologic mode....so it takes care of your problem....
it'll work..