[ctuna]

If you were going to do this one item at a time I would do Amp first, doors second and undeseats last. Why because if you do the subs first they will overwhelm the doors. You will actually get some bass out of the stock underseats with more power they may not last long . All the stock speakers
in the Hi Fi are 2 ohm that means they get the power of an aftermarket amp at the 2 ohm rating. I strongly would advise you to go the Musicar route as they can give you a balanced system . You get all the wire harness , speaker adapters , shims the system is already pretty much setup, it comes with factory connectors its as plug and play as it gets. They won't sell you stuff that doesn't fit or sound good.

JL XD 600/6 is a pretty common 6 channel amp used in this car.