Power depends on the room, target output, and speaker efficiency/specs.
From a stereophile article, here's the specs for the 2.9s:http://www.stereophile.com/content/n...specifications
They're stated as 87 dB/W, and 6 ohms. Depending on what "low power" means, it could be suitable in a smaller space. Emotiva, Onkyo, AudioSource, and many others could all be starting points, but it really depends on your budget. B&K wouldn't be a bad choice, the same goes for Parasound, Rotel, Adcom, etc - I wouldn't buy just based on the name though, especially used; go for functionality/quality over brand names (in other words, if you find a B&K that's beat to hell, don't buy it over a brand new Emotiva or Onkyo).