My 550 loads all the pistol calibers (380ACP, 9mm, 38SP-357MAG, 44SP-44MAG, 45ACP, and 45LC). In rifle it only has loaded 223's, until a month ago. I have set it up to load 22 Hornet. It's 18 years old and does a great job. Once you get it setup right and know how to run it the 550 is hard to beat. However, the question becomes volume. If you don't shoot a LOT of a particular caliber you may not need it.
I load ALL my other rifle calibers on a single stage Redding. For most of my varmint rifles I load 200 to a batch and if I'm ambitious that will take me an entire evening; however, usually it will take me two. Which is good.
The Forster Co-Ax is on my shopping list to replace the Redding. I love their dies.
Good luck.