You don't need to completely remove the glow or remove the transparency in the circle center. Probably better would be to provide different transparency/glow rates where others can pick the ones they like the most. For me a faint glow and transparency will be just fine. If the transparency is too high it's hard to see which one of the stacked objects is the first one. The stacked objects move to the side automatically anyways. I personally use the approach circles to figure out the number of circles in the stack.
Also:
Name: Baka
Color: green
Also:
Name: Baka
Color: green