How to spot a high current amps?

Thanks to everyone for the quick responses. The points of listening to all equipment and never trusting a manufacturer's figures are well taken. Unfortunately, short of buying each individual piece and then reselling it on audiogon, I will probably never be able to hear most of the amps I would be interested in purchasing.

While I think that what I am wondering about is an A/C, not a DC circuit, could I apply P=I(squared)R to figure out how much currrent an amp will push, given a known speaker resistance and output power? Perhaps this is a gross oversimplification that will lead me down the wrong path.

So does anyone have a rough method of evaluating current without physically contacting the amp. All of the aforementioned techniques are sort of "tire kicking"...