Another migraine sufferer here. I too read labels and avoid the things you have mentioned...but may I add (and look out for this yourselves) is FD&C yellow 5 food coloring and large doses of caffienne. I have said that if I ever drink a diet Mt. Dew (aspartame, caffienne and yellow #5, my head will blow up. MSG, btw, can be listed on food labels as 'natural flavoring.' So be careful!!!
I must say, it is good to be able to drink (some) diet sodas now that they are switching from NutraSweet to Splenda. I was really missing the soda! Another huge trigger for me is red wine, which amazingly enough, I don't miss at all.