You will probably never get to the max power on that amp. Even in a comp where you are running the crap out of the system, you are going to hit power compression really quickly, increasing the load seen by the amp and reducing the power it is putting out. For daily driving, you won't get close to the rated power of the amp and keep your hearing. Once you get to the threshold of pain, you have already done damage to your ears. It doesn't take much power to get most subs that loud.
In a ported box, by all accounts that sub can handle much more than the rated power displacement wise but as with any sub, running that kind of power for an extended period of time will have adverse effects on the coil from heat. At those kind of power levels 300 watts over RMS is not even really overpowering them significantly, combining that with the fact that you will never use the full power of that amp, you will be fine.
