Turn it up as high as you want. The only issue you may run into at 0 or above is if you run into a big peak or something like that. Even at full blast, if your AVR is only driving 2 channel you shouldn't run out of gas. I wouldn't recommend leaving it up there for hours on end, but for shorter periods of time having it up high shouldn't do any harm to anything at all. Especially if you've run room correction so 0 represents reference levels. If you're driving more than two channels with the AVR at that volume, clipping may come sooner, but I'm run my onkyo 3009 at full tilt for a few songs two channel and it barely broke a sweat.