I have Canadian version of the GT7+ (no IR blaster) purchased from Best Buy.
I have been using it quite a bit, hours on end, and have not noticed any heat problems. (But then I have not really noticed any heat problems with the new iPad either). My little LG phone sometimes gets warm with a lot of usage.
I have not noticed any unusual hissing through my earbuds with either the music on or off. I say unusual because I listen to a lot of old music from the seventies and the original analog sources always had a slight hiss even after converted to digital CD's. But even some newer stuff sounds clean and clear. This is subjective. Perhaps you can take your headphones to Best buy and try listening to the same music source from the demo galaxy tab 7 + and see if you get the same result.