Try the 6x9s, the IB subs work VERY well, but if you want to save $, or weight, this sacrifices both. You def have to separate the trunk area from the cabin, to get max output, so you need to reskin the shelf to cover all the holes. I agree, 6x9s by a reputable company and a small amp is where its at.
btw, Kicker at one point made a speaker called the f69, freeair 6x9...it was just for this purpose. E-bay may have some for the low low.