In my experience, if there is an LFE input that is being used, auto-on features tend to work better. I have had trouble with the use of RCA inputs though. If you are running high level through it, (which I know the PB-13 does not support), there would not be any issue at all.
As was already noted, some amps don't actually power down much or any when in sleep mode. I don't know if the PB-13 does this, but my PC+ does. The PC+ draws .6 amps of current when sleeping. That was a surprise to see. That's like running a 60 watt lamp 24x7. So...I switch the amp on and off. Remotely switched outlets do that little trick rather painlessly.