I would say have a good look at the builders and styles of boats they build, sadly these days, most boats are built to maximise internal space, and therefore tumblehome is decreased, and more importantly swim and bow lengths are drastically shortened and as a result boats won't swim well, props can't get enough water, and so they can't perform as well when cruising. There are lovely wide beams out there, more of a Dutch barge style than wide beam narrowboat, which would give the space you need whilst still being responsive at the controls.
Good luck with your search, you won't regret it!
Kind regards
Dan