Another 550B user here (over 20 years).The cost of 550B cal conversion kits does add up. I find changing primer types a bit of a hassle. Don't know what I'd do without it though.
That having been said if you've been able to stick with a single stage as long as you have and are on a budget then maybe a Lee turret would work for you. I don't have one (just a Lee classic cast) but this forum sure likes them. I picked up a nice solid older Lyman turret that is great so there are options.