Donno much about how your suggested speakers would work in that scenario, but worth considering is also the way in which your receiver handles reproduction at lower (or 'normal') volumes. If I'm not mistaken Onkyo often employs Audyssey in their receivers, and the finer models have Dynamic EQ (and Dynamic Volume). Sadly it doesnt look like the TX-NR609 has Dynamic EQ? I have this system on my Denon, and at pretty much
any volume level I choose it gives a very distinct and dynamic sound all 'round. I never feel as though I'm missing anything. Reference-levels are a mute issue in my case, regardless of the time of day (or night) I turn the system on. I contribute that to Audyssey. Dynamic Volume is perhaps more a question of taste, and I personally think it works great with television, not movies (dvd/blu-ray).
You should really read more about Audyssey and it's Dynamic EQ in particular. Here is what they say on their website and I can pretty much assure you that the statements they make are accurate:
http://www.audyssey.com/audio-technology/dynamic-eq
http://www.audyssey.com/audio-technology/dynamic-eq"Audyssey Dynamic EQ maintains bass, clarity and surround sound at low volumes letting you enjoy late-night movies and television. Music, movies and games are mixed at high volumes and they’re meant to be played back at high volumes (reference level). In the studio, composers, musicians and engineers hear every detail. But in a home theater, people turn the volume down and sound quality suffers – voices change and bass and surround sound disappear. Audyssey developed proprietary methods that calculate the differences between reference level and playback level in real time. Dynamic EQ is the first technology of its kind to combine information from incoming source levels with actual output sound levels in the room, while taking into account human perception and room acoustics. The result is something never before possible – bass response, octave-to-octave balance and surround impressions that are detailed and accurate at any volume."
Best of luck choosing and setting up your system!