What area are you in? no point doing a full exhaust system on a base model, if money is your issue that is. If it's not go for gold. If you're in sydney, Merrylands budget exhaust did my Catback with canon (xforce) at the end for about 350/450 can't remember now was a year ago.
As far as coilovers, I don't think it's interchangeable unless you change the shocks as well to the type s ones. I could be wrong.