Once upon a time I got most of my brass from one of two places. The first was Midway, and the other was DAC which has now closed shop. It used to be they both were one ad pages in the gun rags and you could get brass in lots of 250pcs. This was nice since you could workup your loads with some and still have plenty left over.
Nowadays, I simply go straight to Starline and be done with it. I order 500pcs and shoot for years. With my magnums I loose more in the field while hunting than I do from splits. Somehow they just don't make it back to the house.
When you set up your die, you only need enough of a bell on the mouth of the case to allow the bullet to feed into it, and barely feel it with your thumb nail. This works equally as well with cast or jacketed. If you set up the die like this you will loose more cases than you will split. It hardly works the mouth of the case. I have been shooting one batch of 357, and one each or 41 and 44mag for going on 4 years and have lost less than a dozen total from split necks.
Also bear in mind you don't need an excessive crimp when you load, only enough to roll the edge of the case mouth into the cannalure or crimping groove on cast. The neck tension should be plenty. Test a few at first and if you can shoot a full cylinder with no movement, that is plenty. When you load them look for any signs of a split or feel for one with your thumb nail. If you not them to start simply stash them in a separate lot, and trim them back just a tad.
Good luck with your rounds, and try not to hot rod them too much, and they will be more accurate and last longer.