Already have a dual sub in the trunk.
Its a mazda 3 sedan.
already have 4 coaxial speakers in the 4 doors.
have 2 tweeters in the dash board and 2 behind the back seat.
all speakers are and will be powered by a 4-channel pioneer amp of 100 watt RMS each.
"""a $200 set of comps can sound just as good as a $2000 set of comps if the install is proper""". i dont think so as many expensive speaker means higher end and higher quality. dont think a 200$ infinity/focal/alpine/hertz speaker will sound as great as their upper lines which cost 2000$ +. or even a 200$ kenwood will sound as great as a 2000$ JBL
I'm literally running a $2000+ set of Hertz 3-way comps on a $1200+ DSP amp, I'm not talking out my ass...
Your HPF setting will depend greatly on what size speaker you are running, how much power they are getting, and the install.
I have my 6.5" MIDBASS drivers HP at 60hz and LP at 350hz. My 3" MIDRANGE drivers are HP at 380hz and LP at 4000hz, and my tweeters are HP at 4200hz.
If you don't have deadened and sealed doors, setting your HP below about 100 is mostly useless and can lead to damage. If you are running 6x9 speakers they generally tolerate a HP of 80hz with no issues.
The pioneer speakers you listed will not do well playing below 100hz on anything more than 20w or so.
You are also wiring 8 speakers to a 4ch amp, so unless you are running a the left doors on ch1, right doors on ch2, left tweeters on ch3, and right tweeters on ch4 you are going to have problems.
I'm trying to help you, either accept the advice and learn why or go blow money and don't care about learning. Your choice
Matt