Possible Clipping/Distortion

Got a 92' S-10 Pickup. I switched out all the speakers, Pioneer 4x6's and 4x10's along with an older DEH-2100 HU that worked okay with my previous system. It sounded good with the music I listen to, Metallic and alot of rock. Then I began building the box for a couple of 12" Pioneer's and began to test the limits of these speakers to see it they can handle the abuse. However with the known flaws of both the 4x6's and the 4x10's I figured I'd be searching/making some crossovers/filters. I was correct, the speakers sound terrible in high bass situations even at low volumes. So I ruled out the clipping aspect. So now is it worth it to get some high passes? Actives, Passives? Should I disconnect the 4x10's in the rear? Comments.
 
So now is it worth it to get some high passes?
Yes, you don't want to feed low frequencies to small speakers, they will distort at higher power levels (you already verified that).

What are your speakers? Full range, 2 or 3-way?
What are you using to power them?

Generally passive are less expensive and easier to implement, especially in a car. If you want to go active, you may require aditional amplifiers for 2 or 3 way speakers.
 
They are all 2-ways. Powered by the HU, no amps. I have did put a passive HP in already and didn't get the results I wanted. I may just try and block 400 hz down on the 4x6's, because they make great high's. The 4x10's I'm less inclined block such a high frequency, but I may block the last 200 hz. Then when the subs are in I may loose a band of a 50 hz total. That wouldn't concern me because eventually there are plans in the works to put in a component setup in there. Any suggestion on filters would be great. Concerns?
 
Yes, there are basic high pass filters visible. I'm going to make a couple of 3rd order 18db filters. The website you gave me is great and I appreciate it. I've been there before, never really saw the calc though.

Do I have to take in acount for the cap already there for the high pass to the tweeter? If the speaker was designed right the design should come out to 4 ohms impedance and it shouldn't matter.
 
Yes, total capacitance in series for n capacitors is 1/Ct = 1/C1 + 1/C2 + ... + 1/Cn

Any reasons why you chose 3rd order? 2nd order is more common, it has 180° phase shift, so if you have issues at the crossover point (dip or spike), reversing polarity of one speaker may help (usually tweeter).

Can you see what is the capacitance of current caps? Any marking on them?
 
I was just discussing this with my brother and he and I decided that I should use a 2nd order because otherwise I'd have to produce a lag network. Also we were discussing possibly going with variable caps, just slightly higher than the one the calculator gave to me of course after I recalculate the value. Another thing, I was thinking about trying is creating all orders on a board with a switch and then I can try each one and decide what I like. Then just leave the thing in there. Comment/Concerns
 
Got one more question and hopefully someone replies. Say I use an actice filter will the opamp serve as a wall between on RC circuit in the filter and the other RC circuit in the speaker? Another question, if I use the Active HP do I need a positve DC and negative DC to hook into the Opamp? All I'll need is a gain of 1 so I didn't think I'd need them.