well
i got 6x9s in my rear, running them on hp, with the bass set to just under half, and have the filter set to about 90hz i think off the top of my head.
my splits in the front i have set to hp, and set at nearly full hz, they still sound great with the 6x9s in the back. just have to play around with it champ and see what you like really!
everyone likes different sounds