In my limited experience, a lot depends on the bike. I'm 5'11" and for years rode a 21" Raleigh Super Course with the seatpost and stem as high as they'd go; it was never terribly uncomfortable, just never felt "right". I currently have a 23" Grand Jubile that came to me equipped with a short-reach (60mm) stem and 38 cm wide bars and was giving me neckaches. Switched to a 100mm reach stem and 40cm wide bars and I'm riding very comfortably now. I've also been quite comfortable, in the past, on 60 cm bikes, and as a previous poster said, on bikes with more upright geometry that were "on paper" 23" frames but very different feel.
From your pics, given where you've set the seat on the Voyageur it looks to me like 23" is certainly the right size for you; try a bike with different geometry, or a more responsive frame.
That Voyageur is damn pretty, by the way...