It depends if it has been tuned already or not.
Assuming it has never been tuned, you're not going to get a huge boost, but you will still get some results. Having the same engine as you, and recently getting a tune myself, I would say you could probably squeeze another 15 (give or take 5) more horsepower out of the car.
A tune will make a much bigger difference when you put on mods--so go get 'em!!
Cams, exhaust, superchargers, intakes (although many including myself disagree on intakes), and more will gain much better performance with a subsequent tune.
You could also achieve better mileage as well.
The thing about tunes is that you will need a new one as soon as another performance mod gets done--minus the intake. My advice is to hold off until you get the mods done so you don't go about doiong it twice.
vince.