With advice from Technic, and MusicarNW. I think I am just going to give in, and put a sub in the trunk.
I am going to try something a bit different for the fronts...CDT components, and a CDT SUBX-120 which is a passive 120 Hz crossover low end will be going to the stock 8" the rest to the components, this will all get a HPF at about 50-60 Hz. I might have to change out the stock 8" to a different midbass driver if it doesn't sound right with the CDTs. But from what I have heard the stock 8" should do pretty good down to about 60 Hz with a better amp driving it.
I will bite the bullet, and put a sub in the trunk instead of trying to get a boat load of bass from the under seat speakers.