Believe it or not, my wife is complaining that the factory 496 HO's are not loud enough in my boat. I looked at the factory tips and they have staggered plates inside the tips that appear to either prevent water reversion or they are some form of baffles. Will changing to an angle tip with internal flappers increase the exhaust sound a bit? My assumption is yes, but don't really want to do it, if I don't get a noticeable difference.

Yes it will. Those are prob baffles in your stock tips. Look in the marketplace... There is a boat being parted out with nice tips for $120 or so.