From sitting in the kop since it was opened up to home supporters the atmosphere in the kop is generated from the back of the stand towards the middle. That's also where the drum is located. It's also been the area where stewards have had to spend the most time telling people to sit down.
So I think it's the right idea to make the upper section standing and that's coming from a season ticket holder in the upper kop who will likely have to move if I don't want to stand up.
By having the upper section safe standing it will mean the make up of fans where the atmosphere is generated remains intact as they appear to want to stand up anyway and then anyone else who does can go in there as well. Acoustically it is better as well as the noise generated will reverberate around the stand and onto the pitch whereas it wouldn't as much at the front.
Plus with having safe standing at the front then extra rows of seats would be lost as there would need to be a clear area before people could see who were sat down.