The thing to be concerned with is the heat soak signal, but even that isn't going to be run so long that it would likely hurt the voice coil, even at full rated RMS power. If we ran it an hour, then it might though. What we'll be doing is to run at 80% rated power, which in your case is 240Wrms. That will not heat the driver to damaging levels, so it will not harm your driver.