only one thing to keep in mind; if you might be getting serious in the future and want a HANS device, you might want to consider the HANS posts when you buy the helmet....they can be expensive or impossible to add later.
personally I use a cheapy motorcycle helmet, whatever fits comfortably. Also get a decent helmet bag and use it, scruitineers will knock back helmets with surface damage, even if it was only a scratch while rolling around in the boot.
BTW that article is very interesting and worth the read....it's not fully relevant to race car use but had interesting conclusions