First I would make sure the improved picture quality isn't due to screen becoming lighter or darker, because that would likely be a PC video level issue. If that isn't the case, make sure your TV has a 1:1 pixel mode and turn off all of the TV processing options, if any are on.
I use an iScan Duo fed into my TV as a PC HDMI input because it is the only way I can get 1:1 picture, as it is a 768p panel. I still retain my display's basic controls, along with white balance, but can't adjust the TV color control. I then tweak that with the Duo's CMS. I'm able to get all dE values under 1.5, so if your dispay really is inhibiting picture quality the Duo can indeed be useful.
I don't have Calman so I can't help you with that.