Efficient monitor to pair with a Sonos 120

I am looking for an efficient bookshelf monitor that will be powered by a Sonos 120 - 55 watt digital amp. I have a Velodyne 10" sub to help with the low end. My room is 12 x 20 with 8 foot ceilings and I listen to jazz, soft rock, and run my tv's audio thru it for movies. I am currently using some B&W CM5's. They are quite good but I think these speakers need more juice to get the most from them.