Can I connect six passive speakers to the Canton Smart Amp 5.1, e.g., two front and four ceiling speakers?

No, this is technically not possible. As the product name of our Smart Amp suggests, the Smart Amp 5.1 has six channels, but these are designed for a 5.1 configuration. The sixth channel is bandwidth-limited and can only be used for a passive subwoofer. The remaining five channels can be used for satellite speakers and the center speaker.