Welcome man.. On the headlights the stock look good but in my opinion look into cft headlights or black housing. Some ppl can pull it off wit the right grill but some can't lol.. Yeah lips are much cleaner, body kits and all that with euro lights just ruin a car especially an Si since it's so clean looking already. Keep Si rims, lower it, add headers, good catback exhaust, and a short ram intake and you'll be riding real nice. Try not to take shortcuts wen building a car. Spend the money and get quality parts.
Btw: adding turbo is gonna run you a good 1,000-2,000.. Some ppl say it's worth it, some dnt. All up to you.