The reality is, and this will save you a lot of frustration in the future, anything beyond 4x MSAA should never be used, unless the game is just really super duper easy to max out.
Many games simply take those options out, but since MSAA is a hardware thing, it doesn't require them to work any harder to allow for higher in most cases, so they let you go higher.
You'll be hard pressed to see any improvement beyond 4x MSAA anyways. You may even want to drop it lower or off for higher FPS.