@joran6
You may have noticed in my signature line, that I do use a powerful external amp along with my AVR. I'm not the only one here who does. If so, why do we try to steer you and others away from a more powerful external amp. Your question has been asked so often, that I kept notes of my previous answers. Here's my own honest experience with adding more power:
It's debatable how much increase in power is needed to hear a benefit. It depends on the speakers involved, the listener's listening preferences, and the acoustic properties of the room.
In my own limited experience, roughly doubling the power (from an old 30 wpc stereo receiver to a 70 wpc Denon AVR bought in 2000) provided little if any audible change. This was with an older JBL L100a speaker that I no longer use. It had average sensitivity of about 88 or 89 dB. When I roughly tripled the power, going from 30 wpc to 105 wpc, I could hear a difference. I've heard similar results going from a 70 wpc AVR to the same AVR used as a pre-amp combined with a 200 wpc external amp – roughly triple the power.
At first, I couldn't say I noticed anything had changed. But soon I noticed that the speaker's bass seemed a little more crisp and firm (less bloated?) on certain musical selections. It was subtle, and depended on the music and the recording quality, so it wasn't always noticeable. Within a few weeks, I started noticing that the cues I used for sound that was comfortably loud and too loud had changed. I could listen at louder levels without noticing that it was uncomfortably loud. When I realized that, I started turning it down.
Apparently, with the 70 wpc AVR alone, I had judged when to turn it down by the amount of noise or distortion I was hearing. When I started using the 200 wpc amp, those cues were less noticeable. It's not unlike driving a car, where I could estimate my speed just by listening to the road noise. If I got new tires, or drove on smoother pavement, those cues changed and my sense of speed was wrong. The more powerful amp was apparently quieter – as in less noisy than the smaller amp – while at the same time driving the speakers louder.
Other than the differences due to greater amplifier power, I've never heard a significant difference in sound quality among different stereo receivers, AV receivers, pre-amps, or external amps. I've looked for that in the past, but never did hear it. I hope that makes sense.