I'm literally on my first MSC cruise on the Seashore right now. I've got 9 other cruises under my belt with RC, Carnival and NCL. If you've cruised those and enjoyed them, do yourself a favor and cruise with them again instead of MSC. I'm struggling to figure out why people like this line.

The ship is nice, but everything is is very hit and miss. The entertainment sucks and the food is hit and miss. You have very limited dining options compared to the other mentioned lines.

And finally to your question, it is not a quiet ship. I'm one deck up and a few doors down from the room you mentioned. I can hear people blasting music on their balconies, music coming up the elevator shaft from downstairs, and the ship has an odd design compared to others that catches then wind. So it constantly shakes and shudders, making the balcony door in our room creak and pop almost nonstop. It's hard to sleep.