RMS Power vs. Dynamic Power

I was looking at some new amps and i came across some MTX ones specifically the 801D and it says:

RMS Power 12.5 VDC                                                       Dynamic Power 14.4 VDC

2 Ohm Load: 500w x 1                                                      2 Ohm Load: 800w x 1

4 Ohm Load: 250w x 1                                                      4 Ohm Load: 400w x 1

Well my question is what do those both mean (RMS Power and Dynamic Power) cause i'm really looking at the 800 watts for what i need to run but will it actually just put out the 500? Thanks for the help

RMS is the continuous power and what the amp will play at all day long as long as it has a 12.5 volt.

Dynamic Power is what the amp will put out for brief seconds while at 14.4 volts.

RMS is the continuous power and what the amp will play at all day long as long as it has a 12.5 volt.

Dynamic Power is what the amp will put out for brief seconds while at 14.4 volts.

Can you define these terms?

I always heard that it took twice the power to make a 3 db difference and that 3 decibels sounded twice as loud.  We hear loudness on a curved scale, curving sharply upward once we get past "quiet".   87 db is considered quiet, but just add 50% of that more and the sound is louder than close up at a rock concert.  The scale defies the logic of numbers.   A good example of this effect is the increase in db's by adding extra speaker cone area.  For instance, you start with one speaker.  The rule of thumb is that doubling the cone area gives you an increase of 3 db.  Well, simple, you say.  Add one speaker to get the 3 db.  Now to get another 3 db, you have to double what you have, going to 4 speakers.  You want 9 more decibels?  How about adding another 32 speakers!  If you started at a quiet sound of 87 db, you doubled the sound at 90 db by adding one speaker.  But to get to just 102 decibels, you had to add another 31 speakers. 

That's the big difference in SPL contests:  anybody can come in with a 130 db system, but to get to 150 db is a feat.  Only a 20 db difference between them, and only a 15% increase, but in reality a huge difference in output.  When it's loud, a decibel counts for a lot.  You see SPL contests break it down to tenths of a decibel.

For your answer, as fuseblower has defined above, always look at the RMS rating, and match that to what you want to achieve.  Published "peak" ratings have no value, if you are in the know.