I skiped on the strong mount as it would place the press too high for sitting. I have not tried a roller handle, don't really see the need personally. I use Lee dies, as I already had them. My only pet peve with the 550, is the spent primer chute. I riged mine easily though.
I don't concern myself with headstamp. The variation also comes from every bullet not being the same length. The die seats on the ogive, not the tip of the bullet. Grab ten bullets and measure them.
I was at the same place, and decided on the 550. I use Lee dies, as I already had them. The powder drop is accurate, and I actually like the manual index.