Personally I use cheap boxers I buy from Crazy Clarks for $4 each or 3 for $10.
They work really well- wick moisture quite well, never chafed with them, they're light and with 3 pair I don't need to wash for at least a week.
When they wear a bit too much I trash them.
I love my Icebreaker shirts but really don't see the point for underwear. Cheapest and most dispensible piece of clothing I carry.
Only merino jocks I ever got were expensive, itchy and the elastic and shape went real fast.