I recently bought S4's from Amazon.
Mine are the real deal though - I think...
If you buy from Amazon, and not one of the third party vendors who sell through them, I would think you are likely to be okay, as they probably really don't want to get sued over such practices, and it would be bad for business generally.
Anyway, I hope Klipsch is successful in stopping this problem, as it is very bad for consumers to not know what it is that they are buying. It also obviously hurts Klipsch, as it makes the resale value of the products worse, as some people will just not buy used products due to a concern about whether the thing is legitimate or not. And used prices do matter, as some people plan on selling their gear when they upgrade.
As things are, I strongly recommend that one only buy new products of any brand from authorized dealers, or you may end up getting a fake. And obviously manufacturers are not going to cover any repairs for a fake.