IT'S A KEEPER.
After considering michaelscott's very insightful and informed comments and caveats and eyeballing his 4K and/or 1080P zone dimming suggestions, I made one last flurry of picture adjustments(short of calibration) and made a decision. This 55l7400u is a keeper in my opinion. For $300 to 500 less than a UHD set or a 1080P with a zillion dimming zones, I got the big, brilliant TV I'd hoped to acquire at the exact price I was really willing to pay.
Here's what I really like and why I'd recommend the set to anyone with objectives comparable to mine: It's a truly brilliant TV-Color density and accuracy are superb-zone dimming and contrast shifts are effective and virtually unnoticeable with the Dynalight setting low or off- the audio system is the very best I've ever heard from any TV, no treble squeals, no hissing, no bass rumble or groan, just clear voices and perfectly balanced background music or sound-more dark scene detail is significantly better than that of my Tosh 46h300u-almost zero input lag- the brushed chrome lower bezel and stand are inobtrusive and attractive.
What I don't like or am not certain about: -the local dimming performance over time from the comparatively small number of zones and overall black level performance. That's it. I going to calibrate the set before I make a final determination about the quality of the black levels.
Last edited by RCA don; Yesterday at 08:10 PM.
Reason: Removal of request for calibration disc information: going with AVS 709