Speaker match for Powernode 2

I’m looking for suggestions for bookshelf speakers in the US$500 range that match up well with the Bluesound Powernode 2. I am currently using a pair of Elac B5s in a second system in my basement. The Elac UB5 would seem to be a natural upgrade, but I am concerned about the ability of the Powernode 2 to drive them adequately.

Is anyone using a Powernode 2 to drive the Elac UB5? Any other suggestions in the $500 range? The Monitor Audio Bronze 2 looks interesting because of its high efficiency. Bluesound likes to promote their sister company PSB, so the PSB Imagine XB could be another option.