Is that a powered subwoofer (tell us the model)? If so, the receiver's power output is not an issue. Even so, when speakers are "rated" for power-handling capacity, you are not rigidly limited to an amplifier that outputs exactly that same amount of power. Those are broad ratings, meant as a rough guideline.
Well, then, there you go. Tell the receiver that your main and surround speakers are "small" and set your crossover to around 120 Hz, and then the subwoofer's internal amplifier will do the low-end heavy lifting. No problem.