Errr.. well, you really should be using true RMS meters... Unless you've got a couple nice Fluke meters (or equivalent) I wouldn't waste your time...
Also, why did you multiply the voltage by two? You should have had the same voltage on both channels. Assuming you did have true RMS meters the calc. should have simply been 30.5V x 10.7A...
Finally, what most people don't understand is that even with true RMS meters you will not be measuring the 'true power' unless you have the amp hooked up to a non-inductive dummy load... what you are measuring with the amp hooked up to a speaker or sub is the apparent power which is in Volt-Amps (or VA)... THAT IS NOT THE TRUE POWER IN WATTS...