First, I'm surprised your agent didn't provide all this information for you prior to booking that cabin so you could make an informed decision.
But with that said, you will more than likely hear noise from the theater below - we did on a cruise on another RCCL ship. However, the shows end relatively early, so it wasn't a big deal.
You may also get some noise from people walking down the hallway to the spa, but you more than likely won't hear noise from the spa itself.
As for the motion, you'll normally feel more 'motion of the ocean' in the front of the ship than anywhere else if rough seas are encountered. The back of the ship will feel less, but sometimes can feel vibration from the engines. The middle of the ship is the best place to be as it has the least amount of motion. However, keep in mind that the Allure is the largest cruise ship in the world with all the latest stabilizing devices and tends to have alot less motion than other ships, especially those that are considerably smaller. So chances are you won't feel much if any motion, especially at that time of year when the seas are usually calm.
If you have any concerns, have your agent check and see if there are any other cabins available that might provide you a better location and more peace of mind. If you booked it directly with the cruise line, they tend to just grab the first cabin that comes up on their screen without regard as to where it is or what else might be available.