Plan 2: Results TBD

After discussion with some stereo experts, my best option is to go with a component system with 6 3/4-inch speakers, and install a slim 50w amp to sufficiently power the larger speakers.
This will require some cutting, but the stock speakers (or seemingly any 4-inch speaker) is not capable of producing enough sounds.
The additional challenge will be installation of the tweeters. I believe there's plenty of area for a "surface" or flush mount, but it remains to be seen.
If I cannot find room to fit the tweeters, I will resort to Focal's K2 Power 165KRC 2-way speakers (also on sale!).

Parts:
Kenwood KMM-BT515HD (same as plan 1)
Focal K2 Power 165KR - 6 3/4-inch speakers $499 USD (~50% markdown as Focal has just rolled out their new line of speakers)
JL Audio HX280/4 - 50w x4 channel amp $169 USD

The parts arrive Wednesday, hope to have them installed by this time next week!