Couldn't find anything in search so sorry if there actually is something.
I recently got a new road bike and the current gears are 12-28 in the back and 50-34 in the front. I was talking to someone in my group about his wheels and said that before the wheels, a big upgrade will be changing the gears. He said to get a 11-25 cassette and switch the chainrings to 53-39. He said I'll easily get a 2mph gain and much cheaper than wheels. I live in South Florida so 99.9% of my rides are on flat roads. Would switching these actually be that much of an improvement? I mainly do group rides in the 20+ speed group if that changed anything.