Although I can appreciate the nice clean look of an On-wall system, given the size of room you have I'd try and opt for some bookshelf M22's as Cat stated to get a little more bass as well as the benefit of being able to place them where they'll sound best.
Sebastien, does your budget include a receiver, or are you going to use the Sony?
Bookshelf are not really an option for me. I already have Floorstanding Klipsch F-1 and some polk M10 bookshelf and I am satisfied with their quality of sound. The only reason I change my setup is to make some place as my new apartment is smaller. I'm gonna keep what I already have if most of people think that on wall speakers would be a big downgrade in quality of sound from what I have and only change my receiver that is getting useless. Note that I do not care if they do not sound as loud since I almost never push the volume high.
My budget include a new receiver as the sony doesn't even take audio from HDMI, probably go with the Pioneer VSX-820 or Denon 790. My budget also include a subwoofer hesitating between the EP125 and EP175, the EP350 not being in my budget range.
