I agree with most everything stated- your getting a lot of advice from some pretty experienced people. As someone with 5 machines spanning 4 manufacturers and two eras I will say that wrapping your head around one manufacturers way of doing thingd and finally feelin like you know the game inside and out- and then switching generations is a humbling experience- you will be doing a lot of learning. To be honest- although I may act like it sucks to not know whats wrong and have no idea how to fix it- its super fun to learn how these work so zero regrets.
Buy what you like and either you will end up enjoying fixing it or you wll not. Just FYI. If you find you enjoy fixing games- your screwed. Many more will be in your future.