That seems like a great excuse to splurge on the 2.5" piping + massives, but on a budget the godspeeds will be fine to get you up and running, and shouldn't be too hard to sell when you take a step up.
Antihero
Putting AMS garbage, and $500 ebay wheels on a Z is like dressing a Victorias Secret model in a Walmart dress and Payless shoes. You're embarrassing yourself.