and do not add on another 4 gauge....just upgrade to the biggest wire you have and save yourself the hassle in the future. also i'm running 1400-1500 rms thru 4 gauge and that's pushing it. anything over 2000 is just a fire hazard.
upgrade your power/ground wire (make sure it's the same size!) to the biggest you can. you can use a distro block/wire reducer if you want to fit 4 gauge in and it'd be fine.
upgrade the "big 3" (stickied in the wiring section).
upgrade alt as a last resort.
set your gains correctly not just maxxing them out. you'll damage both the sub and overdrive the amp.
or let someone who knows what they're doing handle it.
that is all.