I highly recommend Royal Oak's Dargen great helm, it is my current favorite helm I own and Jeffrey Hildebrandt did a REALLY good job on mine, here are some pics he took of mine and sent to me before he mailed it.
[ Linked Image ]
[ Linked Image ]
It costs quite a bit to get but in the end it's worth it, I dont think I will ever get another great helm again after this and I probably am going to get another helm by him in the future.

Yeah, their dargen is in my wishlist, but it is currently bit too much for me who are living in third world country.

So now I am aiming for Maciejowski great helm from someone else first before getting their dargen