You could use the light bulb trick, the same as powering up an amp for the first time except you put it in series with the speaker. I think a 25 Watt bulb is what JBL used in their Pro enclosures. I think it was 27 Ohms so the resistance has to be accounted for, but it is safe to say if the bulb starts burning bright, there is at least 5 amps in the speakers and that is a lot if the woofer is wired direct and also asking the tweeter to work too hard even after the crossover cuts the lows.
Mark
Mark