I have a 550b and and XL650.
I don't use the 550b much, and have been thinking about selling it.
It works wonderfully. has large and small primer setups, the DILLON roller handle and allen wrench set that mounts on the back of the press.
It's great machine, but it tends to sit while I run my XL650
PS - this is not a "for sale" ad. If I decide to sell it, I will post it at my gunclub to sell locally