I have the following on order to replace the stock setup...

Alpine 7894 deck
Infinity Kappa components for the front

Instead of a solid plate to mount smaller speakers in the 6x9 opening, I was thinking along the lines of using standoffs from the stock screw holes to the (small) speaker mounts. This would leave a gap between the cutout and the speaker of approximately 1". But I'm wondering if that would mess up the speaker's response - maybe a small enclosure would have to be built. Apparently some people have cut holes in their rear decks to get the bass out of the trunk.