IIRC, with the Acoustimass setup, the speakers are connected through the sub so the AVR will never see a sub in the setup. The 609 only uses Audyssey 2EQ which does not EQ the sub so not as big of a deal if they are paired together. However, if you were to get the 709 or other Audyssey model that uses Audyssey MultEQ or MultEQ XT, both of which can EQ the sub, that would be a waste of that feature due to not being able to EQ the sub because the AVR doesn't know it's even present.