The Cat 3 rooms are very nice, but with 4 adults and a 16 year old (basically 5 adult sized people), it may get a little cramped. We used the sofa bed for our DS8 and it was more than big enough for him, but 2 adults may be a little crowded. The Murphy bed in our cabin was in the bedroom, next to the door to the balcony, so with it made up and the sofa bed made up, we would have had to climb over one of them to get to the balcony. Not sure where it is located in 8532.
As for noise..... that was our only complaint during the entire cruise. The noise during the night as people walked on deck 9 and especailly the crew getting ready for the day (dragging tables and chairs VERY early in the morning - 4:00am), made for a less than pleasant experience. We complained to the concierge staff and Guest Services, which helped some, but the crew was still noisey in the early morning. I really wish they had designed the ship to not have cabins directly under noisey areas. We have a Cat 4 cabin, under the hair salon, booked for our 4/04 cruise.... hopefully that will be a much quieter location.
As for the perks of a Cat 3.... the concierge staff was very helpful. They were available to make ressies at the spa, Palo's, etc. They had "goodies" sent to our room every day (cookies, chocolate covered strawberries, etc.). As I said above, the cabin was very nice, and the balcony was large. You can order room service dinner from any of the menus (except Palo's) and room service full breakfast, not just continental. There are many threads here on the board that talk about the perks.
All in all..... we would probably not spend the extra for a Cat 3 or higher again. The noise would be a BIG reason. If we couldn't have reserved the Cat 4 under the hair salon for our next trip, we would have gone with a Cat 5 on deck 7 to get some peace and quiet.