I have a bad L4 and L5 and I can sit in my Tarpon 120 kayak for 6+ hours. Paddling a canoe for me is "OK" ... fishing out of it is a back killer. As long as I'm paddling, I'm ok.
I haven't tried the new fancy canoes called The Ultimate but I hear the seats in those are pretty nice. Keep in mind ... they are not kayaks. They are canoes. You take a wave over the bow or side and you better have a bilge pump.