Your planned setup sounds a little wrong to me. You might see show cars with 6" and 6x9s mounted right next to one another, but itdoes bugger all for sound quality. 6x9s really should be mounted to the rear, and they're more suitable for full bodied cars.

If I were you I'd buy some good quality 6" splits and mountthem in the kick panel, tweeters in the corner of the dash. I'd also get a four channel amp and one of those base driver mini subs, both can be angle mounted under your seats.

If your seats are that bad convert it back to standard, then you might even be able to fit a 10" woofer, although that would be overkill.