If your exhaust is loud and drones at highway speeds, 300rpm can make a difference to you. Probably in the grand scheme of things, with stock exhaust, 300rpm isn't that big a deal imo and not worth the expense.
If it were me and I did mostly freeway driving, I would swap them out.
I have 3" exhaust with Flowmaster 40's and 4.10 gearing. It kills me on the freeway, but around town is a hoot! I'd kill for a 3.23 chunk. Well, almost.
