Each amplifier company rates their amplifiers differently. Take for instance most of the cheap amplifiers on the market you'll see these rated for ridiculous amounts of power for their size. Definitely not worth the investment, buy a lower power amp from a quality manufacturer and you'll have better, cleaner, louder sound. E-bay is a great source for amplifiers if you can find a seller that you can trust. I've seen several used Orion amplifiers that originally sold for $200+ sell for $20-$50 with a non DOA guarantee.