Yamaha lists the output at 8 Ohms to be 105 W, and 160 W @ 4 Ohms:
http://usa.yamaha.com/products/audio-visual/hifi-components/amps/a-s1100_g/
It's always been my experience that Yamaha publishes very conservative technical specs.
http://usa.yamaha.com/products/audio-visual/hifi-components/amps/a-s1100_g/
It's always been my experience that Yamaha publishes very conservative technical specs.