Still have my Specialized Sub 6, a helmet marketed on how little of it there was! Scary how little coverage it has compared to a current mtb lid.
Personally, I try to buy from a physical shop so I can try them on. Companies shape often changes, eg I used to always wear a Giro, but the last few I tried didn't fit well.
No need to spend a fortune, but buy a reputable brand from a proper source. After seeing the amount of fake motorcycle gear being sold on Amazon, I'd never buy from there. Also check the date sticker on them to make sure they've not sat for years being bumped from place to place. Proper brands put the manufacturing date somewhere on them.
Currently running a Troy Lee A3, but hard to look past the new Flowline, which is very similar for £100 less.