Nitrous is a good idea, especially considering you already have the clutch. I ran 1.4 seconds faster at the track with a ZEX 55 shot (dry) over all motor. It was a bad day, and my best all motor was only 15.8, but with the 55 shot I managed an awesome run of 14.45 in the 1/4 (and a 9.25 1/8 mile). On a better day I would have been pushing 13's. So just think of what your car will do with a 75 shot. My friend with a GSR swapped Civic EX actually has my ZEX kit now, and with the 55 shot he's high 13s (he also has a CAI, DC 4-1, 2.5" exhaust, and suspension).

Anyways, hopefully you have some skill driving. Are you going to primarily race in the 1/4 or 1/8? That's a huge difference, because some cars can do great down low for example and dont have a lot of top end...for example, I could beat you in the 1/8 but you should edge me out in the 1/4. Take that into consideration when picking certain mods (for example for the 1/8 I would go with the 4-2-1 and for the 1/4 the 4-1).
I have 2 friends with GSR's; one has a 4-2-1 header and 2.25" exhaust; one has a 4-1 and 2.5" exhaust. The first one beats on the second one until the second one starts pulling like crazy at around 80 and passes him. The first one is faster in the 1/8; the second faster in the 1/4.

Again I would go with a dry nitrous kit; I really liked my ZEX kit, simple to install/use and very effective. You will own him even with just a 55 shot, but your car can easily take a 75 shot if you retard the timing a few degrees. Good luck!