You may want to Google that unit, there is a article on Sound and Vision of that RSX-1057. It's 75 X 5 @8 Ohm's continuously. I didn't read the whole article but from what I read it's got issues. Just Google that unit, you'll find info of it. PDF downloads of a manual. That unit sold new for around 1299.00 at the time. It is an outdated unit.
Just a note, new AVR's also have issues. Yamaha's new Adventage line, with their 2.1 HDMI ports, are still locked and owners are still waiting for a promised future firmware update. Denon and Marantz has only one 2.1 port that is unlocked, that I know of. But 2.1 effects gamers mostly if that matters to your needs. If you do upgrade to a new model of your choice do yourself a solid and research what you want and need before you buy may save you from having buyers remorse.