Sooo....or seeeewwwwww.....what is the difference between the 301, 401, 501, 402, 403 and 503 machines??? Does each one use cams? Did each one have an added feature? There is a 402 in a cabinet for sale on our local "for sale" group and I didn't even know they made a 402!! Just trying to sort out these models and if I truly still want a 301 or would something else be just as nice. I already have a 401. Thanks for any help.