The stock amp and speakers are pretty weak so I'd look into replacing those.
Are you looking for a head unit or are you going to stick with the stock one?
Replacing either or both the head unit and amp will require some PacAudio harness adapters to allow the aftermarket equipment to interface with the stock CanBus harness.
As for subs, the 2-10's would sound good with the right amp. I agree with PorkChop. The MTX Thunderform is also a good choice.
You can see some info on my set up here....