sirquack,
The reason that I suggested using external amplification to power m80's with the Onkyo is that a couple of months ago an Axiom owner reported having issues with his Onkyo 805 shutting down quite a bit with his m80's. This occured even when not driving them at very loud levels and I don't think that his room was huge like yours either. Furthermore, the power supply in the 805 is much beefier than the one in the 705. I own the 805 and am very happy with it. But, if I were to upgrade my m22's to m80's down the line I would definitely get some monoblock's to power the m80's even if they weren't shutting the receiver down all the time. This is because if I'm going to spend $1300 on a set of front speakers I want to make sure that I am getting all the performance possible out of them. But, that is just me. As you mentioned, if the original poster is not having problems with the 705 going into protect mode then there is no need to upgrade right now or ever if he doesn't want to.
- Nick
