[AceX]

You'll be fine with 8ga wire. Realistically, that amp won't pull enough current to require that large of a piece of wire for power and ground. Take power from the battery, and place the fuse no more than 12" from the terminal connection. Try and keep the fuse as close to the terminal as possible. You can use a ring terminal to make the main connection.

The "remote" wire should be spliced into the acc. wire (in the column) or fuse.

For speakers, I generally like to use 16/14 for speakers and 10/12 for subs. It just depends on the power I'm running. I recommend using 14ga on the speakers and 12 on the sub. No particular reason one way or the other, that's just how I roll.

As far as wiring the speakers, the sub(s) will HAVE to run off the rear channels, and nothing else should be run with them. Run the 6x9's and dash speakers off the front channels @ 2ohm.