After reading the good/bad/ugly for all of the Dillon Presses (one of which is quoted above) and after consultation with my dealer, I found the 550 to be optimum for my needs. Load about 7 different cals (mostly 9mm and .380). The change over from one cal to another is an absolute snap with the 550. Starting with primed brass, I load about 650-700 per hour. Since I bought the 550, I have loaded about 25k rounds.
I went to my dealer to get the 650. After we talked about half hour, he told me that he was going to cost himself some money but he said my situation screamed 550. His reasoning was virtually a carbon copy of the research recited above. I do not regret getting the 550 and see no chance of going 650/1050 any time soon.