your car isn't very fast first of all if it's stock.
go drive a M3 or STi and see if you will still say "fast" to your car.
intake is intake, nothing special.
just a tubing with a filter at the end. ebay ones are just fine. i'd rather get SRI.
you gain 3 things. alot of noise, a little in mpg[i gained about 3/gallon on city], and a little if of power gain that you won't notice with just the intake. well..yeah.

ebay intake is just fine.

and wtf is JDM springs? go with a name brand, and get shocks and spring at same time and put them in at same time. might as well run on proper setting and don't bitch about how "boucy" or "stiff" or "uncomfortable" it is.

do you even read any reviews or search about the item you are about to buy?
if you don't, then you will end up bitching or crying or like it. and most of times, you'll end up bitching and crying as do most people who don't search a bit before buying.

i'd recommend Koni or KYB shocks with Eibach or Tein or Koni springs. mix and match any of those companies and you'll be golden.

good luck

hoyoung02