I would not be concerned with motion. Sailed on this ship 5 times and never experienced what you might have felt on smaller ships like Disney. As for noise, I'd agree that you'll want to steer clear from theaters. As for the SPA, it typically doesn't operate late at night, appointments normally conclude by 9pm at the latest. So, from a sleeping perspective, I would not anticipate a noise issue on deck 6 near the SPA. You might have some noise from the Aqua Theater as it's probably more likely to hear from that?