If you have a local shop go try some on or purchase a few online in different sizes and return the ones you don't want. Also the sizing charts provided by the manufacturer aren't exactly accurate, size/fit varies from brand to brand and model to model and is dependent on the shape of your head (I am an L in the Simpson bandit, M in the Simpson devil ray, L in the Zamp FSA-2, and M in the Zamp RZ-22).
I only have experience with 350+ helmets, but I like the Zamp RZ-22, love the Simpson Bandit and Devil Ray. If you look at Zamp FSA-2 make sure it is labeled SA2010, some old stock will be labeled SA2005. Fit and comfort is up to the individual and difficult to say how another person will like it due to varying head shapes...