Sub wiring

^^ Right.  Using both sets of terminals on the amp is making a parallel connection, so two 4 ohm loads connected this way makes the amp perform into a 2 ohm load.  Otherwise, the way most commonly done is to connect the subs together in parallel first, then connect to the amp using only one set of terminals.  It's exactly the same either way.  It will be the rating of your amp at  __watts X 1 @ 2 ohms.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

nope, may as well use both sets of terminals, generally looks cleanerdouble-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer