I don’t really get the beef about the latency. You can make the canvas match the output of the Io by changing the frame offset in the preferences. The only downside to this is if you monitor audio out from the computer for some reason, it will be off from the canvas.
Oh well, I hope the DeckLink works for you, I do agree with Tony though. Since you already had an Io, why not get the Kona2 and keep all the video interface hardware coming from the same company?
-mark