Pulley is best bang for buck and the increase is hard to replicate once done as other mods wont give as much power and will cost more !!
Nice list of mods to work through:
1. Pulley, belt and plugs
2. Intercooler
3. Manifold
4. Camshaft - newman is what ive got
5. Mynes tune.
That should see you to around 240bhp IMO...
Ive got a black 16% pulley for sale if your interested
Intercooler is a good idea and good for peace of mind IMO - first mod I did
Things to watch out for have been mentioned above really but suspension bushes, steering column / power steering issues and coolant header tank splitting are the main things that I can remember...