Hi,
So let's call it a cool 1500 square feet approximately, which is smallish, and your listening position is 8.5 feet. Just knowing that, you likely don't need anything more than your AVR. Great reading here:
What benefit does a user get connecting an external power amplifier to their A/V Receiver? This article gives guidelines when it may be time to consider external amplification for your A/V system.
www.audioholics.com
So let's approximately calculate some of this:
I went with the 89db sensitivity rating on your mains (it was rated at 89db to 92db, so I went with the lesser value to show the worse case scenario). Two speakers (reinforcement). Near a wall (reinforcement). 60 watts (the max of your AVR sustained with all channels driven). At 8.5 feet.
This puts 104.5db at your listening position as a peak SPL. Way louder than you want to listen. Even at 1 watt, your setup and distance will produce 86.7db which is the reference for a movie theater roughly, and has headroom to go to 104.5db, or a 17.8db change. So greater than 10db is perceived, psychoaccoustically, as double the loudness. So you have plenty of dynamic range left in headroom here for transient spikes in response.
Of course, all of that is +/- a bit based on other things in the room, room response itself (nulls, modes, reflections) and room correction (if applicable). But it's just to illustrate that your system at 60 watts is way plenty for your space and distance. And if used in stereo mode, has gobs of power that you'll never even tap into.
Very best,
