anything from buffalo is a fantastic bit of kit, used the special 6 shirt in anger across the globe and its by far the best shirt of its type.
Arktis mammoth is possibly better value for money but they are out of stock in plain green and apparently it will be a couple of months before they have them again.
I looked at the FORTIS one, and my personal opinion is that its too thick, too warm, too heavy, too expensive and waiting time is long.