Power handling capability of original Quad esl 57s

After many years of hearing about how wonderful the original Quad esl 57s are, I finally found a near mint late serial number pair. I'm in audio heaven! I used to own the 63s and the 989s, and these are much better ( in the sweet spot).

Now my question: what is the power handling capability of the 57s? There seems to be some confusion here. According to the original manual, it is safe to use any amplifier as long as it does not produce more than 33 volts at any impedance. This is an interesting specification because it does not differ from the 63s.

Ok, let's do some math. At 8 ohms, 33 volts into 8 ohms gives us
33^2/8 = 136 watts! At higher imoedances, power must drop, so at 30 ohms, the speaker can only take up to 30 watts.