There are lots of people here with progressive loaders, and we all have opinions. Understand that all opinions and advice is worth what you paid for it!
I've had a Dillion 450 later upgraded to a 550b since the mid 80's, back then I did a 20,000 batch of 223 that I still have about 6500 and they can come out fine. With any progressive you'll have a slow start up speed and as you build "muscle memory" you will increase speed. the key is to not go faster than your zero mistake rate. When I did my large batch, the 450's load rate was considered 450 rounds per hour (the powder and priming were hand activated) with the 550b you can honestly get 500 to 550 rounds per hour (it has to do with primer, powder, and bullet supply. On the 1050 press we go through components so fast, a second person loads primer tubes and keeps the powder measure, bullet tray and case feeder full). I have a case feeder on my 550 (they are for handgun ammo only) and it won't make loading any faster, only it will make it easier.
There are little kits for each cartridge you load that include the shell plate, indexing buttons (3) and powder fennel. These parts can be bought separately also. When you go to another cartridge you may need a whole kit or just a few parts (I just change the powder funnel for 9mm from 223), of course adjustment need made. The "Tool Head" can be set up and never touched again (a very nice feature) or you can change dies every time. Once I understood how to change and adjust a complete tooling change, it was less than a 20 minute job with primer size change and shell plate included. It is up to you on what you spend your time and money on! In wood working the saying is measure twice and cut once! double checking every detail saves lots of headaches.
Concerning dies: Since I did my big batch, Carbide 223 dies have become affordable. Hollywood brand were several hundred dollars then and RCBS's are less than 60 now.(the neck area still beds lubed!) on straight walled cases Dillion's are the very best for any progressive press! I own 4 sets of 45ACP dies of 3 different brands and I found out to use Dillion! On tapered and bottle necked cases, most brands are fine, just avoid real short dies (Lee dies are sometimes too short to get a locking ring on -- short pistol dies mostly).
Dillion has changed some of the ID numbers or letters on shell plates since I bought mine but they still work the same. The older ones were machined to specs to be more universal (like 223 and 380 and 9mm), today I think they are listed as separate! On my press and shell plates 460 S&W, 454, 45 Colt, 44-40 Win, 44 Mag, 44 Special, & 44 Russian plus 303 British and 30-40 Kreg (and a few others) all use the same plate, BUT Dillion would gladly sell you one for each! Same for 10mm Auto, 40 S&W, 7.2x39 Russian, and 6.5 Carcano, 6.5 Creedmore, & more. Do some research and save. The conversion parts will not go down in price, so buy the ones you will need sooner than later. I bought every shell plate they made in 1986 except 8mm Label and 45 auto rim. there are some new ones but the only one I might need is a 500 S&W.
Primer tube filling machines range in price from several dollars to several hundred. I have heard so many complaints about every one of them, I just ended up with 10 tubes of both sizes and spend the time loading them to old fashion way (you'll need some cotter keys for these).
If you would like any more unsolicited advice or have questions about 450, 550b or 1050 presses, feel free to PM me. Ivan
