For athletes Under Armour kit is, if not the best you can buy is very close; it really is top notch quality. I've been using Under Armour gear for running for years and it's remarkable. It's so light, supportive and retains almost no moisture. Wash the kit and it's dry in minutes. Most kit on the market now is synthetic but none of the others seem to match Under Armour gear for keeping you dry.
These boxer jocks are made from exactly the same materials as the sportswear and hence are virtually weightless, very supportive and comfortable and will keep you dryer than any other brand of underwear. They are very stretchy in every direction so it's quite safe to go a size down if you're in any doubt. They look great on so for me you can keep your Calvin Klein's, the name might not have quite the cache but for quality and practicality these simply can't be beaten.
Sometimes you get what you pay for; with Under Armour you're not paying so much for the name (although they do sponsor the Welsh rugby team and Spurs), but you are getting very high quality and practicality. For men's underwear these really do tick all of the boxes.
I'll give this range of underwear five stars. They may not have quite the kudos of those designer labels but that isn't high on my list of requirements. In every other important respect they are superior to just about any other make of underwear that I have owned.