your amp can run the subs but you are the one running the system to the dirt clipping the hell out of the signal out of dissatisfaction of the output. So what you need is to get a fck ton louder so you dont ever run into this issue again and keep the amp and sub at safe operating levels while still getting brutal amounts of bass. Also never ever mention max power again EVER unless you want everyone in the car audio community to make fun of how nooby you are. its always RMS wattage ratings that matter.
so order of importance
1s thing you can do is change the enclosure to a more efficient enclosure, do a properly done custom ported box built exactly for the sub's electro mechanical parameters and the car's acoustics in mind. AKA you need a skilled box builder that really knows how to get you loud and sound good.(ones that have proof of winning modern day spl contests doing big numbers with big bandwidth)
2nd thing, bigger amp for more headroom and to account for impedance rise. Right now wired at 1 ohm, you are getting 2-4 ohm power out of your amp. Thats just how the physics of a coil moving through a magnetic field works, the impedance does not stay at 1 ohm, it'll change at every frequency and the amount of power you actually get is FAR less than you can ever think of. If its the Pioneer GM-D9601, you are at best getting 500 to 800 watts total for both subs wired at 1 ohm after impedance rise. If your hertz subs are 750 watts RMS(not max) you'll need at least a 2000+ rms amp to get the max performance out of them. However this is definitely 2nd place compared to the box.
3rd thing, upgrade electrical so you can handle the power. Also clean up your signal, if its an old outdated head unit with low preout voltage, you'll have weak bass from that as well.
4th thing, upgrade to beefier subs/add more cone area.