I agree with Stevie and Bill. Could the answer be that these cabs can handle the output of a typical "800W" amp, because that amp is only actually capable of delivering a burst of that wattage at a narrowly defined frequency range and over a few milliseconds? An amplifier that could deliver 800W RMS continuously over a wide range of frequencies would smoke them, but that doesn't happen in the real world because such a beast probably doesn't exist. As stated above, watts alone are pretty meaningless. Some manufacturers, such as Naim Audio (before you say it, I appreciate that they don't design kit for musicians), rate amplifiers on their ability to deliver current, rather than wattage. Would that be a more realistic measure?