Bill's right. It's pixie dust, really. Even RMS wattage claims are pretty meaningless. They may tell you how much an amp will heat an 8 ohm resistor for a few milliseconds, but into a reactive load like a speaker and across a full range of frequencies, that all goes out of the window. And that's before you start factoring in speaker efficiency, etc. Best to ignore all claims and audition stuff in real-world situations.