No, the amplifier in the subwoofer never powers speakers, it only powers the driver in the subwoofer. Apparently you feed the signal into your sub and one branch takes it into the sub amp to drive the sub, while another branch goes straight through into the speaker. Unless the speaker is connected to some other amplifier it's indeed self-powered. Note that the info you linked states that the satellites are "60-watt powered".

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Enjoy the music, not the equipment.