cheaper to turbo yes. but increase in displacement not only adds quite a bit of torque and hp at all rpm, but it allows the motor to be able to handle more hp without being a completely strung out high-rpm-only race machine.
but you want some expensive stuff...
http://www.tomei-p.co.jp/_2003web-ca...x-com-eng.html
now granted you may have to be creative as they are supposed to go into a RWD car but id bet you could get them to fit.
(btw 114 yen is about 1 dollar)
but theres parts EVERYWHERE for SR20s, you just have to look and be a little creative. almost any silvia/240sx SR20 part will fit your car, except like possibly the clutch/flywheel (not sure if they fit).
now this kid has an HKS exhaust...id call HKS, Apex'i, and other companies and ask them directly if they make one for your car
http://community-2.webtv.net/Racer_X_91/Jims01Sentra91/