Higher Voltage to Amplifiers?

[4doorrocket]

Pardon my ignorance... I'm shopping for Amplifiers and I read different RMS outputs based on Input voltage. Standard car voltage is 12v right, but some specs show increased Amplifier output with 13-14.4 Volts input. How do I convert the input from stock 12v to 14+?

[Accord Man]

well, P=E*I

but that wont give you true figures with todays amps..

the battery is 12v, but your alternator puts out around 13.8V.. And sometimes close to 14.4..