I've got the Pioneer 6x8 plate components in my truck. They sound pretty good. Better than regular coaxials, and just shy of decent true component speakers.
I'd suggest getting a hi-pass filter for your Pioneers if you've got too much bass. I think that 75Hz to 120Hz (depending on your musical tastes) would do.
You can get some bass blockers from
www.partsexpress.com for a couple bucks each. For that cheap, you could experiment with different x-over points too.
