If memory serves, the On/Off button is mechanical so if you plug it into a switched outlet that can handle the amperage and as long as you have left the power switch in the on position you should be good to go.
No harm to the amp. The amp will go through it's normal turn on cycle.
There are lots of better amps as well as lots of worse amps out there for $800. I don't have the slightest clue because I don't know what you plan to hook them up to. Does the $800 include the preamp and tuner?