Ok, after implementing the advice given to use Vector2's as keys I've got one last query/problem:
How should I go about handling angle wraparound?
For example; given the 2 points (DISTANCE, ANGLE): A(100, 10) and B(100, 350). These 2 points are close by but will not be considered by operator comparision (<=, <, >=, >) to be close by.
Any ideas how I could handle this?