I understand that different amp manufacturers use different methods to rate their amps output wattage (peak vs RMS) but I have a question for those in the know of how these ratings are determined. I have a mid-70's Acoustic Control Corporation 450 head. According to the owners/service manual, power output (continuous) across a 4 ohm load @ less than 5% THD output is 170 watts RMS ; peak power output (instantaneous) across a 4 ohm load @ 5% THD output is 450 watts. How does this translate to the way amps are rated now-a-days? If this amp was being marketed now, would it be listed as a 450 watt amp? My limited knowledge of amp ratings has come primarily from reading posts on this board, so I'm hoping someone here can clarify. From what I have read on Talkbass, it seems like Acoustic was merely describing how amps actually work, as in a 450 watt amp is not continuously pumping 450 watts into the speakers. Thanks in advance to anyone with some insight.