I personally don't recomend wireless at all, but make sure they have a good range. The ones I have have about 5ft of perfect signal, 10ft of good signal and so on. But they are IR so anything in the way of the emmiter and I get nothing but static. I'm not sure if they make RF(I'll look into it) But I think that would be a way to go, exept I'm sure their would be interference and noise mixed in with your audio.
I would advise checking out a large online retailer, and see if they have user reviews. In my opinion, all these facts and numbers and such hold second to word of mouth.