That amp has no where near enough power to properly power your "properly ported SUB". If it's a dual 4 ohm sub, just wire it to 2 ohms and run it on the 5th channel. Otherwise, search on here and read up about how to set gains and such. You should have LPF selected and set around 85, subsonic set a little lower than the tuning of the box(if your amp has that option).