Start with this:- direct-port nitrous injection
- four-core intercooler
- ball-bearing turbo
- titanium valve springs
In all seriousness, good gains can be found with an intake, exhaust, HFC/test pipes, and a custom tune. You can find even more power with a SC kit or twin turbo and go FI. I would also recommend an oil cooler.
Looks are subjective so do whatever you like.