Sorry, I'm not the one to ask. You'll need to spend an hour or so reviewing the many discussions here and on the wiki, and decide how they align with your own priorities.
If you do that, you'll find that I'm usually pooh-poohing open-air solutions and recommending the Amulet or VoxWav.
That's simply my opinion about what makes sense for a reliable, stress-free voice control experience that doesn't involve yelling across the room over loud background music or screaming kids.
A boundary mic could work well if you're willing to combine it with some kind of "on/off" trigger (i.e., keep the mic off by default and use a simple middle-button mouse click or a button on your remote to trigger a command that turns the mic on and system volume down when you want VC to listen to you--then be sure to turn the mic off again).
I'm not a believer in any "always on" fantasies. Although I personally have had pretty good success using VoxWav Pro in always-on mode, I've never tested it for longer than half an hour or so, and I happen to live in a really quiet environment. I know it would drive me crazy to try to make it functional in a noisy household/crowded room.
