As far as amps being rated correctly, a manufacturer can choose to rate their amps correctly by continuous or peak. I agree good amps go with the conservative less flashy ratings.
According to Wiki: "Continuous power ratings are a staple of performance specifications for audio amplifiers. In its 1974 Amplifier Rule meant to combat the unrealistic power claims made by many hi-fi amplifier manufacturers, the Federal Trade Commission prescribed continuous power measurements performed with sine wave signals on advertising and specification citations for amplifiers sold in the US. Typically, an amplifier's power specifications are calculated by measuring its RMS output voltage, with a continuous sine wave signal, at the onset of clipping—defined arbitrarily as a stated percentage of total harmonic distortion (THD)—into specified load resistances. Typical loads used are 8 and 4 ohms per channel; many amplifiers used in professional audio are also specified at 2 ohms.
"Continuous" power measurements do not actually describe the highly varied signals found in audio equipment but are widely regarded as a reasonable way of describing an amplifier's maximum output capability. Most amplifiers are capable of higher power if driven further into clipping, with corresponding increases in harmonic distortion.
"Peak" power is the maximum level of work or energy output that is measured during an observation period. Peak power here refers to the maximum amount of power an electronic component can possibly handle for an instant without damage. Because of the highly dynamic nature of many audio signals (e.g., music, which accounts for an alternative name, music power) there is some sense in attempting to characterize the ability of equipment to handle quickly changing power levels. But, how small an instant is a matter of some variation from observer to observer and so a peak power rating is necessarily more than a little indeterminate.
It always produces a higher value than the continuous ("RMS") figure, however, and so has been tempting to use in advertising. Generally, whatever the definition of instant used, distortion is also higher for an instant. For instance, an amplifier (especially a surround sound receiver), may be rated at 1,000 watts peak power, but the harmonic distortion level might be 10 percent under those conditions.
According to the Lexicon site, "The Hyundai Genesis Lexicon 500 watt power amplifier provides 11 channels of pure power distribution for exceptional performance. All channels are driven at 40 watts with two dedicated subwoofer channels at 80 watts each. All 40 watt channels are driven at 20Hz-20kHz, 10% THD"
As I suspected the distortion rating of 10% in our 500 watt rating in our Lexicon amp would indicate the rating is peak power. Also as Lexicon states the 10% rating is just for the 40 watt channels. The sub channels at 80 watts since they dont make a statement on those are probably worse.
As I stated in my original post most automotive amps (and by that I meant factory supplied amps) use peak as their measurement and not continuous. It appears our Lexicon amp is one of them and that is why the earlier poster was wondering why 500 watts did not sound like a concert.
However you want to rate our amp, the Lexicon in the Gen is a very good stereo overall and at the price point we paid for our car pretty hard to do better compared to the competition.