Yeah, I'm not going to bother disputing the patently absurd notions that screen size should max out below 70"... As to the core question, it's Sharp and Sharp right now.
Samsung is promising -- for the second year in a row -- a 75" model. If they deliver it, the price will be high and the performance most likely won't. Figure $8000 MSRP +/-.
Panasonic may deliver a larger TV later this year. Emphasis on "may".
Otherwise, it's Sharp and Sharp.
There is no difference in HDMI cables. If you can see the picture without visible dropouts or sparklies, the cable is working at 100%. No other cable will display a better version of that picture. You're simply wrong if you think there is a better digital cable than one that is already working.