I also own the F8. Its a good solid machine, but a little noiser than the 680. I'm not wild about Zoom Products, but the F8 is at the top of the food chain. It is powered by internals and depending on how many channels, sound checks, and the like, you may be able to get a full long show in. I use any 12v power brick. The input is a type M barrel connection.
I got custom input cords made with a 90 degree bend on the inputs.