It is an external PSU, as my PC is a mini case, so I am not 100% sure what it is. If you know how to check, let me know.What is the exact model of your power supply? Knowing the rest of your hardware specs would be helpful as well.
In short, yes, you "can" upgrade from one to the other, but knowing the other information would be necessary in order to determine if you "should" do that or not, and whether or not you'll be likely to have power issues.