I have to admit, my first thought was also "NO! Don't touch it!", but who am I kidding, my Coupe had the standard tape deck in it when I brought it too.....
1. Definitely agree with pretty much everything the guys have put down regarding engine hardware. I'd go a 14B turbo with big16G turbine housing and probably look at a 2.25 - 2.5" exhaust, my mate is running this turbo and exhaust setup on his 4G93T powered Coupe and it hauls hard. The big16G might be a bit laggy on the 1.8, but that's upto you to work out I guess and what you like.
2. If you're looking to do brakes, definitely go for the twin spot caliper and bigger disc upgrade IMO rather than stuff around on the standard ones (this may involve going to 15" rims). Do the EVO brake booster and master cylinder too.
3. If you're really inclined, front and rear strut braces make a bit of difference on hard cornering
4. Decent rubber on your wheels.
Save your suspension money until you learn how your car handles on the road and track with the new engine hardware setup. Do a few track days and talk to the professionals to get some pointers and advice as to what would best suit your needs and ability (and budget!!)