Here's a simple formula to determine the Deckard's output power at a given impedance: divide 81 (voltage squared) by the impedance of the headphones (ohms) and your answer will be in watts (81/ohms=W).
So to run through our headphones, the output power of the Deckard into each is thus:
20 ohms (Sine, LCD-X/C): 81/20= 4W
30 ohms (EL-8): 2.7W
70 ohms (LCD-2): 1.15W
110 ohms (LCD-3): 740mW
200 ohms (LCD-4): 400mW
With that you can determine output power at any impedance.