X pipe questions?

Hey everybody, I finnaly got a job....so tomorrow I am going to the bank to get a loan for a new toy. ..but before the payments hit....I want to put one or two mods on the Mach 1...I need to know what is the best "bang for the buck" off-road x pipe? And how much will it cost...And is there ANYTHING that I'm going to have to buy so my SES light doesn't come on? Thanks guys...And if anyone can post some sound clips I would be very thankful for it.