10" sub in the factory box???? Holy lack of airspace, batman!!!
Anyway, running LOCs (Line Out Converters) is the easiest and by far the best way to do what you wanna do. You'll get FAR better sound with the LOCs than you will with a high level input. High level input, in my ever so humble opinion, sounds like crap. I ran LOCs on my stock 99 Cutlass deck and it made my sub VERY happy...piece of advice...if you can, get the adjustable ones and have the dude at the car audio shop set em for ya. It'll raise the signal going to the amp so you don't have to run your gain so high....it'll also give a much clearer sound.
That's my $0.01. But then, what do I know?