I agree with dropping a goalie. With only 3 goalie categories and only one of them requires quantity of goalies, a fourth goalie is potentially unnecessary. Though I might consider looking for a trade depending on the need in your league for a goalie.
As far as who to pick up, if you're looking at this year I don't know how much impact any of them will make. Morrow has not been impressive in the ahl this season http://www.pensburgh.com/2013/2/10/3...all-joe-morrow
Also I'd have to guess with a healthy letang and Niskanen in a few weeks, morrow will go back down
Gardiner might have a shot if he can get back to the NHL. And I too am wondering where larsen's development is going.
So with it being anyone's guess for this year, I'd probably hold Larsen who should be a stud someday