I'd seriously consider the 550 depending on what you're loading and the powder you're using. I really like mine and load 223 and 6.5 Grendel on it. I don't have much issue with that except the brass prep. I figure once I get a 6 Dasher built I'll be getting a tool head for that to see how it goes. I don't typically shoot enough on my bolt guns to make it worth it though. The one thing is that I'd have to size, clean, trim, all of that then run it in the Dillon. I don't see the need to run it in the Dillon at that point because it's all just primer, powder, and seat. Not too much work on a single stage. If I got a new single stage it'd be a Co-Ax, if I got a turret it'd be the Zero.