Bibs should really be sized by height.

For men, if you are 6', get a LARGE unless you like your balls being squeezed in a vice- the bib straps run a bit short. Even a large is a bit on the small side- for the Ypro3 bibs (they are cut to fit while on the bike, not standing).

Castelli's US distributor is a local company here, and I've found some great deals... I am ambivalent about eh KISS shorts- the seams really dig into my flesh, and several seams started to fray while they were still new.