help wireing amp

Your amplifier is 2 ohm stereo stable, which means you can hook up all four of your speakers to the front outputs on the amp, and then use the rear outputs for the sub.  You also maximize the potential power output of your amp.  The only drawback to this approach is that you lose the ability to adjust the fade between front and back speakers--they are treated as one because they're all actually playing off the amp's front outputs.  So when you're up front workin your head unit and fade to the rear, you'll be fading to just the subs.  Some people (myself included) actually prefer this feature cuz it lets you listen to just the subs, and no output from the other speakers.  Good for test purposes, or to see if your sub is making weird noises.  And it makes it a lot easier to fix rattles in the car caused by the bass cuz you can listen to it loud without hearing the treble.  When you're done listening to just the subs, just put the head unit's fade control back to the normal spot and everything goes back to normal.

Your 4 channel amp has separate crossovers for the front channels and the rear channels, and the cut off frequencies are adjustable. I'd put the 2 channels for the subs on low pass.  Set the front outputs' crossover frequency to just below what you set for the sub channels, but put the front outputs on high pass.  This way all the bass will go to the subs, and all the mids and highs will go to the 4 main speakers.  Overall efficiency of the amp is maximized.  You might want to play around with the frequencies a lil bit to see what combination sounds the best, and to make sure that you're not missing out on any particular frequencies (e.g. if you set the subs for low pass at 250 Hz, and the speakers for high pass at 350 Hz, you'd be filtering out frequencies between 250 and 350).