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Pioneer SA 9800 Output?

I currently have a Pioneer SA-9800 integrated amp, pushing JBL L166 speakers. The amp is rated at 100W/channel. If I run a second set of speakers (A+B mode) will the effective output become 50W/channel? I have some Boston Acoustic A-60's not in use, rated at 60W max, which would work fine in the living room. I just don't want to blow them out with too much power from the SA-9800. Thanks in advance. RPK