You'll enjoy better signal-to-noise ratio if you send the amp a relatively hot signal (as long as you don't clip anything) and turn the amp gain down to suit your needs. The gain control on the amp is basically an attenuator; it has no effect on the maximum power capabilities of the amp. It's best to optimize the levels of the rest of your system (unity gain) and then turn the amp gains (volume) up only as far as you need to. Turn the gain all the way up on the amp can be nasty. (Hum, buzz, and hiss..etc)