s13s come from the factory with a noticeably larger front gap than the rear. If you maintain stock height with the proper coil setup (konis + ground controls are said to be the best), you'll have a fully functioning suspension. People lower their cars for looks more than anything. If you want maximum performance, replace your shocks / struts and keep your stock height. If you do lower your car, you should invest in adjustable suspension pieces to correct for having a lower roll center.
http://zilvia.net/f/archive-faqs/270...-assembly.html