Hi Tweety, I've never been on that ship, but I took a look at the deck plans, I don't think that location is so bad, as insides go.
First off, there is no point in paying to be on a higher deck. The view from the inside of an inside cabin is the same no matter what deck you're on. And if it's motion you're worried about, the lower you are, the less you feel the ship's roll.
Also you are not actually all the way to the back. It's sort of at the middle/back. Which is good in that you won't feel the pitch of the ship much as compared to those cabins nearer the front of the ship.
You will likely feel some vibrations, as most ship do have some. But that is usually only siginificant at certain times, like when the ship is pulling up to the dock or away from it. That's not much time over all.
Also think about how this cabin sits in relation to other places on the ship. You are only one or two cabins away from the elevators and stairs. When you think about the places you will be walking to, when leaving the cabin, this is a great spot. A few steps from your door, and you get on the elevator. The elevator door opens an you are already at the buffet for breakfast. At dinner time (with luck on your dining assignment) the elevator door opens and are already at the dining room. Very convenient if you ask me.
And when it comes to noise, those low deck cabins, surrounded only by other cabins, make for the quietest ones at night. I think you're in a fine spot. Don't waste your money on a change, that may not even be an improvement after all.