i own 2 of those off of 2 hdc312s. Nobody can stand sitting in my car right now it's so loud.
We stress tested the HDC3s on and off for 3-12 sec burps for about 3 hrs when setting all test tones and measuring xmech, bla bla bla.
They never got hot, the amps nor the subs.
Both are beasts.
I'm bout to get a 250A alt and i have all powermaster, 2 D5100s and 1 D3100.
At full tilt with the car off, batts voltage drops from 13.0 to 12.6 immediately then the longer you play, the more it will drop.
After burping for about 3 hrs on and off that day, we finished with the lowest drop down to 12.3v, jumped up to rest at 12.6v until they were charged back up.
Also- my impedance curve is higher than most because i have my 2 12s in a smaller box than practically anyone else. The lowest the subs have ever seen is 1.76 ohms but that is at moderate volume. At full tilt, the lowest they've seen is 2.21 ohms so they may not be going full tilt on the power, but the pressure feeling it does to your ears drives people out of the car very quick. This is another reason why they can handle the power so well too due to the impedance curve i have.