That is my comment ...correct me if i wrong

1st change your 4ch amp,
take out the rear speaker (may interupt front driver sound),
change woofer & the amp which push woofer (ur woofer SPL woofer may very hard)

Agree with driftmeister, SPL amp no matter how you tune it... The sound hard to be clean & clear...
SQ sound is clean & clear, you can hear the vocal & musical clearly.
If not why prokick amp so cheap le...?!

If the rear speaker still same loud as or more loud front speaker, it maybe become noise at front. So disable it or direct connect to HU or use lower the rear spekear volume.

Ya... When you open up the amp...U will know what kind of component use inside Prokick...
If you know electronic, u will know what is the difference between prokick amp with Helix, TRU.... lo..also why the price prokick so cheap..

For me, clean mean I can listen the music & vocal separatly & clearly without interuption...
Dirty mean sound noisy... Moslty SPL, I can't hear vocal clearly

Corect me if I am wrong.

Woofer need to be solid and can come to front seat..hehe
Maybe boardtune can help...

Even how you final tune the existing amp, it only help a bit only.
If you need tune as SQ amp... I can say it really hard..!

3 way need to align the tweeter & mid positioning & also tuning...!
This is the most hard way to do it..maybe need cut the dashboard or door or kickboard...