The Cobb off the shelf maps do require you to have a stock airbox. technically you can run an aftermarket intake , but its basically at your own risk.
Defi Gauges arent worth the money in my opinion. Ive had them before and sold them to get some money for other more important things.
Check out
www.prosportgauges.com. They have a new line of gauges including Peak gauges and they dont require a controller like defis. They are also brighter. Ive got these gauges and honestly I like them more than I did my DEFI's.
A good rule of thumb for gauges if you get three is Boost (if you dont want your stock), EGT, and Oil Press. EGT gauges are cool, but if I was you I would get a widebang gauge setup. Either PLX/ AEM/ or Innovate Motorsports would be fine.