^ what he said

Also, another possibility for the exhaust, as far as what I've heard and read about, is the Apexi WS2. Not too stock-looking, cause of the mirror-like finish, but it's not that loud unless you realy step on it. Have some fun here with listening to the sounds, but keep in mind that for a lot of them, it seems as though the mic was somewhere close to the muffler, so they'll all seem a bit loud, and some of the sound qualities are weird, but you'll get a general idea as to how they sound.

as for headers, you could do what like 75% of ppl do and get the DC Sports header, or if you wanna go more expensive (can't vouch for whether they perform better...) there's the GReddy and Comptech headers.

Intakes...yeah, if you have the money, and you want something relatively stock-looking and not really loud, I'd say the comptech would be your best bet, as GSSR said.

Here are some online sites you can take a look at that I found that seemed like good places to shop:

www.modacar.com
www.summitracing.com (these ppl really like their customers...)
www.passwordjdm.com (some really cool stuff here, but more expensive)
www.nopionline.com
www.performancecenter.com
www.kteller.com (some crazy thing there...)
www.rev-auto.com (some decent prices on some parts)

there are a whole host of sites out there...so just shop around and see what you like!