You would mainly get a CAI for the sound. It's probably negligible performance benefit at best, same goes for other "performance" bolt-on mods. If you change the ride height, or increase the downforce or other things, it will upset the car's balance. Now personalization of the car itself is a different story. It all depends on your use of the car? Is it your weekend car/daily driver/track car? I wouldn't be altering the engine components wildly if you need it to get you to work every day.
For me, I'll be dropping in performance summer tires (General G Max RS in 235/40ZR18), lowering springs, a rear sway bar (Whiteline) and vinyl wrapping various pieces and a Hondata tune whenever I get around to it. My plan is to have it as my summer car as my current 8th gen Si is still kickin - albeit a bit rough around the edges and would be perfect for harsh Canadian winters.