Droopystop, I didn't think too much about wearing a helmet until an instructor handed me one to wear when I started to learn aerobatics, and then I didn't think too much about it afterwards, until I started to look into buying an aerobatic share, at which point I discovered how useless my passive headset was in a Pitts.
So I was looking into buying a decent headset which revealed good reviews for the Clarity Aloft. Which I could just buy and be done with it, however if you read some of that really long helmet thread linked on the previous page, there are some scary stories of not just crashes (there are some of course) but bird strikes as well where the pilot has lost an eye!
I think a helmet sounds like a good idea, and with the CEP option you are effectively gaining the benefit of the Clarity Aloft at the same time as some degree of bonce-protection, as well as whatever extra passive attenuation you get from the helmet shell.
The Clarity Aloft is about £425 and the Gentex helmet in Kevlar with CEP is £765. I'm leaning toward getting a helmet at the moment.