I think a pair of Reference 3A MM DeCapos would be a good choice. I had a pair in a slightly smaller room and they were very good on 3.5 watts/channel. The Coincident UHS series may work well too. It's really going to depend on the listening volume and your choice in music. Large scale classical may be an issue unless you go with a super efficient speaker, which typically means a large floorstander....
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