IMO i wouldn't worry so much about the surrounds. Your mains and centre will pull alot more power and if you take the front three load off the receiver, the AVR will have plenty of overhead for the remaining surrounds.
I'm planning on putting my Anthem MCA30 in the HT room to power the front three while the new Denon will power the 4 surrounds. If i were going to add more surrounds into a 9.2 system, i would probably consider more external ampage.
Unless you expect to have ear bleeding sound in a very large room such that the AVR may be driven too hard. This situation always seems rather rare. I cant' say i've seen anyone's typical HT room be so large that you need a ton of power.
