Well after getting thoroughly confused at all the options out there online, I decided to go to my wonderful LBS and try to work with what they had in stock. Glad I did! Never would have guess my head was a large! And as I told my BF when he told me I could have measured my own head, even if I had done that, if I saw it was in the large range, I would have thought I did it wrong and bought a medium! Even in the large range we had problems finding one that would come down as far on my forehead as it needed to be. SO, I ended up paying a bit more than I planned (but the LBS threw in what I call a 15% suckers discount) and got the Giro Atmos. When I asked my son (23) if I looked less like a mushroom, he laughed and said no and that in fact he would buy me a red one with white spots for Christmas. (think Mario Bros).
Well, even if I still look like a shroom, I have more vents and a better fit with a lighter helmet. I got a nice neutral white so hopefully this experience can be put on the backburner for another three years.

L