Well, first: putting the Replay in front of the center speaker would cause the sound from the speaker to get deflected/muffled by the Replay. Plus you have the fan sound mixing with the center speaker.
So I wouldn't recommend this orientation for that reason.
But, I don't think putting a speaker behind the Replay would be a problem. On top of or in front of the replay might be problematic. I believe most of the magnetic fields of speakers are focused around and behind speakers, not in front (but I'm not an expert, so I could be wrong on this).
But, I don't think putting a speaker behind the Replay would be a problem. On top of or in front of the replay might be problematic. I believe most of the magnetic fields of speakers are focused around and behind speakers, not in front (but I'm not an expert, so I could be wrong on this).