I couldn't agree with Steve more! Finding a lid that fits is second only to buying one that provides quality protection.
Additionally make sure if you are ordering online that you know what the manufacture date is. Helmets have a life span and the discount might be because the shelf life is getting old. While there is some debate over this (usually with people that don't want to have to buy a new helmet), I believe both Arai and Shoei recommend replacing at 5 years old.
I know now that even helmets have life span thanks for that. I think its not about expensive the helmet is, I think its all about how protective the helmet is. Find a helmet in local store that fits me well, search for it online, find a reliable site and purchase one.
Thanks for all those replies. It helped me a lot about helmets.