OK, I was all set to get the Rockchucker Master Kit, but my buddies said no, that I'm going to want a progressive press. I had wanted a Dillon 550, but don't want to wait as long as it will take to save... So, RCBS says that with its "Piggyback 4" unit or some such, the Rockchucker press can later be turned into a progressive. Well, not understanding in my mind precisely how an add-on unit can turn a single-stage into a progressive, I need someone who knows to tell me specifically whether the RockChucker with the Piggyback is a GOOD progressive press, for when / if I go that route in the future? Do it have any deficiencies over buying a progressive from the get-go? So, bottom line, get the RockChucker now (as I want to), or save for the Dillon or some other progressive? Thanks!