The most power you can safely use is 125 watts rms per channel into 8 ohms. Higher quality amplifiers will have more current that can drive and control the speaker for better quality. The lower in impedance the amp is able to double power tells you that it has more current. You can use more than that but you will run the risk of damaging the speakers.
AVRs power ratings have become pretty sketchy. They all have to reach the magic number of 100 or more and they can get very tricky to do that. Many receivers will produce 25-35% of the max rated power spec when used under normally.
Since the speakers are fairly efficient at 91db for 1 watt at 1 meter you can power then with as little as 20-40 watts and get them fairly loud.