I own a Dillon XL650; it's the next step up from the 550B; and, in my opinion not necessarily a, 'better press'. For many years reloading was my real avocation. Many times I came home from the range honestly believing that - more than pistol craft - I was going to the range only to produce more reloading work for myself. (I built some beautiful ammunition!)
I don't see anything on your list that I don't have or haven't used. In fact I've got a lot more equipment than what is described. (RCBS Case Prep Station, Sidewinder Tumbler w/ double barrels, a large spare parts inventory, and much more trimming equipment than has been mentioned. I've, also, got large and small press-mounted powder measures, a separate micrometer powder measure, and two precision powder scales as well as 24 extra feed tubes that I prefer to use instead of an automatic case feeder - Which is way too fast for my liking!)
I think the question needs to be answered; 'How much do you like to reload?' If you're like most shooters I know, reloading will become a restful and addictive hobby for you to pursue. I know that, many a time, when I've had a bad day I like nothing better than to get on my reloading bench and just make ammunition. It's a hobby you have to pay careful attention to; so there's no time for distracting thoughts or worrying about, 'other stuff'.
If I were just starting out again, and had the money, my own answer would be; 'Yes!' I'd buy all of the items that salesman recommended. (Obviously he's a serious reloader who likes a nicely set up reloading press as much as he likes a fine gun.)
PS: Just read through your list again; you're going to need a powder scale for sure; and, if you use other than Dillon dies on the 550B then make sure you use hexagon shaped lock rings because they're much easier to adjust. OK!