Don't take this the wrong way, but that amp wouldn't do 1000 watts if it was struck by lightning.

It is a two channel amp with a 40 amp fuse rating, and like most mainstream two channel amps, their lowest acceptable impedance is 2 ohms stereo or 4 ohms bridged. My guess is that you wired your subs to below this impedance and your amp said no-no.

You can't necessarily 'get' your amp to run at the impedance you want by bridging it. The impedance of each subwoofer's coil will designate how you should wire the subs to the amp. If the subs are dual 4 ohm, you can either run in stereo, one sub per channel at two ohms, or bridged at 4 ohms. If the subs are dual 2 ohm, you are limited to only running in 4 ohms stereo with that amp which is the 170x2 rating, so if thats not enough you should look into getting a mono amp that runs at 2 ohms.

All that being said, your truck should handle that amp without a problem, and even should handle a 4 channel just fine also, and 4 gauge is plenty for that amp as well. So overall, it is probably a good idea to have professionals do the job.

EDIT: Matt beat me to it when I was typing my big reply.