I have had a UN60D6420 for over 2 years and have always had AMP set to Clear. I prefer to have my Denon X2000 do all video processing from my two sources, which are a DirecTv HR34 HD DVR and a Sony BDP-S5100 BD player. I have the BD player set to output the native resolution on the disc, and I have 24p output set to off because it causes unpredictable lip-sync issues on my set up. I have been generally happy with the Clear AMP setting, but have always hated the ghosting of balls in football (the great american kind) baseball, golf and the puck in hockey. Any setting other than Off is un-watchable for me due to the various reasons that have been discussed in depth already in this thread.
I decided to try some testing using my Spears & Munsil 2 disc to see if there are any differences between Clear & Off and the results surprised me. I used the video test that has 2 wedge shaped images made up of white lines, with the wedge on the left oriented vertically and the wedge on the right oriented horizontally and they move around the screen in a clockwise direction, and they do so in various cadences.
With AMP set to Clear, there were varying amounts of artifacts with some I would call severe, in the wedges depending on the cadence, but when I set AMP to Off, the artifacts lessened by a large degree on each and every test regardless of the cadence. The artifacts were mainly flickering or flashing and were easily seen. Selecting any setting other than OFF (Clear, Standard, Smooth, Custom) produced the artifacts, with some settings better than others depending on the cadence, but all were worse than Off...............So based on this test I have been using Off for the last few weeks, and will do so from now on. The pros of AMP simply don't out weigh all of the negatives it produces.
Samsung UN60D6420 ~ DirecTV HR-44 ~ Sony S5100 ~ Roku 3 ~ Denon X-2000 ~ HTD Level TWO Towers ~ HTD Level TWO Surrounds ~ Power Sound Audio XV15