Not sure on the components - but as for the subs, a dual 4 ohm sub will wire down to two ohms. A D2 sub will wire to either 1 ohm, or 4 ohms. From then, you run it at the 336 watts, and then a second one will be wired in series to 2 ohms, taking the full 600 or so.
Yes, the IDQ should fairly easily keep up. Go with a good sealed box, or even IB, I would say - though that would be much more work than you'd like, I'm sure.
If you can, do 6.5" components. A much improved midbass response from them, due to the extra cone area. If you have problems with the grill too close, cut a baffle, of MDF preferably, and put it between the grill and the door, using new screws that match the length. I don't know how the car is set up, but that's what I'm imagining.
Otherwise - I'm not sure of a good rec to give you. I'd say the ID components, but those are a bit above the price range.