At least you don't need a boost gauge.

If you have a good tuner tune it, I don't think you need any gauges, personally, but that's just me. You can always add them down the road. Maybe grab an EGT next time you fuss with the headers.
I really don't know dick about N/A Subarus. However, I can tell you that my car would run fine on the stock map since it's a bugeye (well I'd probably want to ditch the MBC or never drive under partial throttle...), but I'd imagine that I'd be giving up like 30 WHP and the smoothness of a custom tune. I'm glad to hear that you intend to get your car tuned once you do the cams. Can't wait to see the results.
Are you going to get tuned for 91 octane?