OK, seriously, enough of the heat inuendo.
The display uses 250w calibrated according to Cnet at 55" (so it will be less for a 50"). It appears to be the most power-efficient Panasonic plasma ever so the notion that somehow it won't work in some application that a Panasonic plasma would ever have worked in before is a "conclusion in error".
Is that more than a current LCD? You bet, it's about 3x what a current LCD uses.
It's also less than a 3-year-old LCD uses.
Heat is not some magic function of plasma televisions, it's a function of laws of thermodynamics. A 55" set is about 20% larger than a 50" set. Because power consumption has historically not seemed to track area perfectly, I'll guess a calbrated 50" uses somewhere around 200-225watts. (Note: It can use much less, and it will in standard mode. Most people won't use it in this mode, however. It can also use more if it's run in Vivid mode, which also won't be done by any normal people.)
Oh, and the temperature of the store has absolutely no effect on the laws of thermodynamics. If you take a lamp with a regular light bulb to the south pole and place your hand on it after it's been running for about 30 minutes, your hand will most assuredly burn. The same lamp will burn your hand at the equator too.
The heat being released is a function of the electricity consumed and the portion of said electricity converted to light and the portion converted to heat. An LCD TV using LEDs as the light source is efficient at making enough light with relatively little heat loss (LEDs actually get hot, but you just don't need very much power to get light from them). Plasma TVs are much less efficient at making light without also generating heat. More power is required to even generate the light in the first place and a fair amount of said power goes to electronics that give off heat.
This is not magic, it's physics. Some models of plasma TVs are slightly more efficient at making light than others, but given how few manufacturers are left at this point, most are fairly similar in their efficiency.
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.