time for me to sound like a broken record again. only 16" to fit the 330's calipers is the AT Italia type 5 rims. other than that, you have to go w/ the 17s to clear the front calipers.
205s or 225s are the recommended specs. i'd say 205s if you see a lot of snow in the winter, 225s, if you get mostly cold weather but not much snow, because wider tires would help out in the dry traction dept.
as for staggering tire sizes, don't. you have no need for it. and also if you have the same size set, you can rotate them for the following year, prolonging your winter tire life, only if for another season.. at least try to anyway..
i'm actually gonna get my hands on the dunlop m3s this winter. for some reason reading about blizzaks, i didn't feel as confident w/ em. any inputs?