quick power/math

I know there is a formula to figure out the maximum RMS power possible from an amp at 12v, but I cant remember it. So if the amp has a max draw of 120 amps what is the most RMS power it can make at 12v, assuming an efficency rating of 70%.double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

Input is VA. (P=VI)(Watts) Output is input x efficiency (ie, 0.7 in your example).    Vehicle voltage can be higher (eg, 13.8V, 14.4V etc) but whether that increases, reduces or doesn't change the current input depends on whether the amp behaves like a resistive load (hence 1450W output in your case), an SMPS (ie, the same 1008W output) or current-limited (1210W output).