Best Built Boats?
It might help for you to state your budget for this purchase. For example, two boats I would suggest as being up to the task are the Allied Seawind II, and the Southern Cross 31. Both fit into your arbitrary size range, and both boats are very capable of blue water sailing -- assuming there are no other maintenance issues with the particular boats you find. But I have no idea if they fit into your budget.
I agree with Jeff H. that all the formula stuff is interesting, but ultimately no indicator of quality. This seems to be a more common thing for folks to want to hang their hats on what some formula says. But the best criteria is examining a boat thoroughly for how well it was made, how well it''s been maintained, and what did the deisigner have in mind for it to begin with. Not many designers of production boats set out to design something to go around the world. Most design something more suitable for "coastal cruising" which in itself is a nebulous concept, but that may be good enough for what you want to do assuming the boat you find doesn''t have major problems.