I have a PowerQuest 34 and it has tons of headroom, plus A/C & heat, hot/cold water, a STAND UP head, and a huge v berth. I am 6' 1" and I don't have to duck going into the cabin. Once inside, I only have to tilt my head or bend slightly. . . lots of room.
Beware of published headroom "specs"!!! I have been on Donzi 33's & 38's and they publish lots of headroom, but for the life of me, I can't see where they get those numbers!!! Before some of you flame me; I am NOT trying to trash Donzi, instead I have personally been on them, and the headroom advertised is not indicative of their actual headroom. Also, I am sure they are not the only ones with this type of spec. Go get in the boat that interests you and see if the space in that cabin is what you want.