The temperatures for your 660M is a tad on the warm side, but nothing to be concerned about yet. Once it becomes regularly in the high 80's, you should start thinking about doing a repaste, but for now just keep an eye on the temps and continue enjoying your G like you are doing.
Removing the bottom cover paired with a cooling pad will drop load temps anywhere from 5-11 degrees.
Using a cooling pad without removing the bottom cover will drop load temps around 2-4 degrees, while removing just the bottom cover will drop temps around the same.
You don't need a cooling pad with these laptops, they more or less just need a good paste job and they're golden.