up market underwear

[Costi]

Sybin, boxer shorts are traditionally made by shirtmakers of shirting cloth or special underwear cotton (or silk). Shirtmakers do not deal with the upper part of the body only - they also make pajamas, for instance.
Boxers should fit well to be comfortable, so they don't bunch up or ruin the line of your trousers. There are cuts and styles that are unavailable RTW. The fact that they are not for everyone to see is no reason to give them less importance than to any other piece of clothing.

[Rossini]

Sunspel or Zimmerli. On the shirtmaker front, Robert Emmett has some nice patterns and the boxers wear well.