your concerns are very good. Your 6 units can be two different courses or two similar courses, as long as it covers to become 6 units.
I would suggest you look around for your future requirements and see what types of courses you are planning to take later on. Look at the courses and check their prerequisites, and see what you need to have in order to take them. Its definately important to look ahead and have a general idea of what to take.
It really depends if the other econ course (Econ 1bb3) is a prerequisite for things you want to take in the future. if not, then if you are interested in psych, then take that.
its nice to have a variety sometimes, and develop new skills and learn new things.
this probably didn't help much, but you know best what your interests are and what you want to learn in the future, so plan from that.