If you can splurge a little, Dillon makes great dies that really seem to compliment the press, but like most things Dillon, spendy (but worth it in the long run IMO and experience) it/they can be. A few days back I checked the ram on my 18 y/o 550B, and it has absolutely no slop, wobble, or perceptible side movement at all when pressed very hard in several positions and ram heights.
By contrast, my less than week old brand new RCBS Rockchucker Supreme, already has (had out of the box) ram movement/minor ram slop after loading less than 100 rifle rounds, and is well lubed and clean. Also the toggle is miss-cast on one end, and it won't allow the ram to center in the fork, and the fork is binding against the ram. No slam against RCBS per se, as this press replaces my 30 y/o RCBS Jr, a lot of my dies and other goodies are RCBS, and they have been very fair the very few times I have contacted them; just the same, I'm not getting the total quality vibe from the Supreme that I do from my 550B. One real treat I like is loading rifle rounds on the 550... So smooth and effortless, and the results every bit as accurate as any SS press I have used.