Turbo or non-turbo?
If you have a turbo a remap will get you to near to 325 on its own. Do some investigation to see how close to 80% duty cycle your existing injectors are before changing them, but my guess is that you will probably need to upgrade them.
A cold air intake, if properly designed and installed, won't do any harm and should provide cooler, denser air.
Get the car remapped only after you have completed the planned mods. You should see 325 without having to go to the expense of replacing the turbo. However, if 325 isn't enough.............
Make sure that your cooling system is working properly as the extra power will produce extra heat. 25% more power produces around 25% extra heat which will have to be removed.
Non-turbo. A remap will get you around an extra 20-25bhp. A less restrictive cold feed intake will help you to get to the 25. Bigger injectors won't give you more power unless you can increase the amount of oxygen in the combustion chamber or the existing injectors are maxed out.
A sports cat may add a couple of BHP, don't believe what is says on the box! If you are lucky you may see close to 290 with the above mods. How would you provide the extra fuel for the nitrous?