I remember reading Ian Farrier's comments on what he would consider a bluewater for his
line of boats: F-36 and up. I also have read that he has some issues with what Corsair did to his F-36 design.
I have never heard anyone comment on the Geminis being anything other than coastal cruisers. As for affordable catamarans that have circumnavigated, or at least made a trip or two across the pond, I would look at the Prouts. The Seawind is a popular Australian design that looks like a very nice catamaran, but would be a bit pricey.
How about this for a definition?: Force 9 capable; beating to windward in that instead of getting washed up on a lee shore.