The 661 will have plenty of power for you. I’ve been using one for a few weeks now driving my 4 ohm speakers while waiting for my Marantz 8001 to be repaired. I can’t pin the volume without it tripping out on me, but it definitely plays louder than I can stand. I did some experimenting when I initially hooked the 661 up. I was able to reach sustained db’s of 95 with peaks up to 105 db at 12’ away from my mains. It would play louder, but I could start to detect some clipping above 95, so I backed it down.
The 661 is really a remarkable little receiver considering what it can be bought for. It does so many things right that other high end receivers don’t do at all. It’s a great bargain and you won’t be sorry you bought it, which is not something that I can say for most of the other stuff I’ve wasted money on. The one little quirk I don’t care for, is Yamaha decided to make this receiver default to an “auto” extended surround mode whenever you turn the unit off. When you turn it back on and want PLIIx enabled for 5.1 sources, you have to manually enable it. There is a discrete IR command for this, but you won’t find it on the remote. You will need a programmable remote.