Well I can relate to never being happy with underwear. I'm about 5" limp, it varies a lot but I've measured right at 5" to 4", so depends on temp, etc. Its not very big around while limp, but its enough that I can't fit in any underwear I've tried very comfortably. I got some of the "Life" brand boxer briefs made of lycra I think, from walmart but those are among the worst as far as pressure. Briefs hold me in place good, but they create so much pressure it gives me a stomach ache after wearing them all day. I prefer boxer briefs, but after I wear them a few times the crotch gets stretched out, and my dick ends up hanging down my leg.
I just purchased a pair of the Jockey Pouch boxer briefs yesterday and I am wearing them now. They are a huge improvement over my hanes/fruit of the loom/life/chereskin/ etc that I have tried. Not as big as I'd like, but so far everything is staying in place and its not nearly as tight.
It makes it bad to have a 32 inch waist and be reasonbly endowed because you can't really wear a size large cause they are baggy on the waist and legs, but a medium offers little room in the crotch
I'm on a mission though, I will find comfortable underwear.