GTO-608C..... end of discussion. exactly what your looking for, signed/sealed & delivered, have installed them in my vehicle, am super happy! As for the A604 Amp, haven't heard it but lots of people have highly recommended it. So if possible, get a demo & then decide for yourself. Price around 6 odd grand, inst incl....
Polk stuff is more for a typical genre of music, blues & jazz to be specific. Thats my personal view.... One thing is for sure, they are not versatile at all, meaning, not for all types of genres of music.