I don't know if you will get any sound at all. The receiver has no reason to send audio out of the HDMI going to the TV. It well might be delayed even if it did.
>>Thanks for the reply. I had assumed that the current HDMI that goes to the TV still transmitted sound to it, even though I had selected the AV Receiver and Dolby to be the sound source in the room.<<
It would not be a boosted center channel anyway. The soundbar would play either LR front or LCR front channels. It would screw things up.
If you need more center than you can raise the level in the speaker set up menu of the receiver.
If you wanted to use the soundbar instead of your center channel the right way to do that would be to use a speaker to line level converter. That would lower the center speaker output of the receiver so it can be safely connected to the aux input on the soundbar.