I dunno, I gotta disagree with George on this one to an extent. Trading in and getting a new car is great and all, but there's nothing better than looking at a finish product that you worked on and saying "Damn, this is clean as hell." A 200SX SE-R isn't a bad car and the SR20DE in there has potential. If you love your car and take care of her, then she'll last you a lifetime just like any new car. Besides, new car payments suck @ss.

Back to your original question...

For modification order, it all depends on what you want to do with the car. Since your primary focus seems to be on handling and braking, I would probably work on suspension first. This will definitely give the car a new feeling and you'll love the results once everything is broken in. Brakes are a good choice, but if your stockies are doing good, then I wouldn't worry about it too much until later. Maybe some Hawk Pads or something.