What freq to X-over 2-way 4" two-ways?

im having a little trouble coming to a final number as far as what value Cap to select for a High-pass filter for my components.

i have six 4" two-way Infinity Reference throughout my car. with a full signal, they distort and crackle Alot. The mids and highs are very bright and dont fatigue w/ these speakers, which is right in-line w/ reviews ive read. in accordance w/ that aspect, the Low end reproduction suffers so i want to block that out.

The Tweeter part of the two-way function has a 50v 3.3microfarad cap inline. reverse calculation makes me think that the Tweeter is crossed in at 12000hz but thats on a 4ohm speaker. the 2-way speaker is 4ohm total though. so maybe the tweeter is 8ohm and the mid range is 8ohm. if thats the case, the 3.3microfarad cap in series w/ the tweeter would make it cross in at 6000hz... does that sound more typical for a Tweeter?

since the total load on each channel is 4ohms, i figured that a 400hz crossover would be adequate for preventing low frequency distortion and crackle. but im not too sure for These speakers in particular since they seem to be especially inadequate for low end response... so should i cross these 4" speakers in at a higher frequency like 600hz or 800hz to prevent any distortion? that would mean that im either going to use a:

100microfarad for 400hz HPF,
66microfarad for 600hz HPF,
80microfarad for 800hz HPF

those figures are for 1st order/inline 6db rolloff per octave.

btw, im supposed to NOT use electrolytic/polarized capacitors, right? Bipolar caps are to be used in car audio filters?