Well, what if u was to get an amp thats puts out say, tiwce ur subs RMS and hook it up to ur subs but on liek a posivtive output of ur amp, put a rehostat(however u spell it). Turn the rheostat down to half way point so ur sub will recive its RMS then whenever u compete u can turn it up full and burp it at twice the watts. Is this possible?
You already have something that accomplishes this. It's called a volume knob.
All you need to do is determine what level on your head unit would allow the amplifier to provide RMS of the sub on a 0db tone. Make a note of what this level is, and don't exceed it. Then burp away when you want to.
plus some amps like Alpine's V12 and Zapco's C2K have features that allow you to trim the output peaks to match your speaker ratings, to avoid overdriving them.