I have a pair of 550's and do not run a powder check die on either. If I had the freedom of an extra station, I might be tempted, but I wouldn't rely on it 100%. I believe simplicity and having control over what you are doing is more important. The 550's make this very easy. Never had a squib or a double charge.
I run a Pacific 366 for shotshell loading. Having 8 things happening at once, where at any given stroke at least 4 things bad can happen: primer doesn't drop into the holder, shot charge doesn't totally drop, crimp starter doesn't form a proper crimp, and making sure I add the wad - all which have happened a few times. While my 366 is fast, reloading on a Mec 600 Jr. is a lot more fun.