For those of you who have multiple Dillon progressives - what was it that drove you to buy the second (and third)? Is it a desire to be able to do high volumes of 2 or 3 calibres that you bought them and leave them permanently setup that way? One for large primer, 1 for small?? I've got a 650 and I've bought 4 or 5 tool heads which really helps, but I always hate changing primer size... 