I am finding this out the hard way. I just "upgrade" from Integra dtr-6.4 to Integra dtr-6.6 to take advantage of the zone2 preout to supply my Miller Kreisel K9 which has an amp plate. The subwoofer signal appears to be full range based on the output of the subwoofer. Also the the low pass filter control on the back of the subwoofer doesn't seem to help.
So... it's back to using two receivers.. I noticed the newer Integra now add a center channel and composite video for zone2. Where is/ Does anyone know what is being sent to zone 2 and if it changed at some point? 6.9/7.9 dropped the sub preout 8.9 kept it and it's back in with the 70.1 etc going forward.