If you settle on a 550B, I have an extra quickchange toolhead assembly with toolhead and powder measure that is gathering dust. I set up for 308 Win and quickly decided that I prefer loading 308's single stage, so it's unused and gathering dust.
I'd be happy to sell it to you for $75 to help out. It has the measure, toolhead, and powder die, no stand. PM me if you're interested. Pics available, just ask.