I don't know if this helps any, but I use a 47" Samsung 650a as my primary computer display for gaming, and am very happy with sharpness and colors, and blacks are decent too.
I connect from the PC's Nvidia card to the TV's HDMI2/DVI input via HDMI, and name that source "PC". IIRC, Samsungs have a certain input that's designed for PC viewing, but that input changes model to model - on the 650a its HDMI2. I would bet if one of your HDMI inputs also has the DVI option, that would be the input to use for PC. Doing this turns off some picture processing, and disables a few picture options like sharpness and color tweaking. The picture mode I leave on "Standard", and everything else is pretty much at default. Text looks sharp.
One major change is to go into the Nvidia control panel and under Desktop Color Settings change the Digital color format to YCbCr444 (from RGB). Sometimes this needs to be redone after re-installing a driver.