A good rule of thumb, is look at the fuses. The Extreme has 2-30amp fuses, or 60 amps. R-O-T: take the fuse rating, multiply it by 6, that'll give you the power it actually does. So 60x6=360. 360 is the actually RMS power that it will do. D-class amps you can multiply time 9, since they are more efficient. So in the case of the Bazooka, it has 3-20amp fuses, so it should do the same power.
There is a big, long formula for figuring out actual power, but that will get you close enough.
You see how your subs have an RMS power and peak power. Throw the peak/max power in the trash on anything mobile audio, because it is a made up number by the manufacturer. Concentrate only on RMS power ratings, that's what matters. Max/peak power usually is twice what the RMS power is (or close).
I have installed both amps, and there is a reason that the Xtreme one is more, its a slightly better amp.
Ok, my fingers hurt from typing
, gotta go to work, hope that helps...
Keep the shiny side up...