Cant run a stage one map with a downpipe, VERY bad idea. If you put a DP on you must run a stage 2 map from something.
Back to the OP. Like Kirt said I run my AP 24/7, mostly as my boost gauge, but I also monitor other things at the push of a button (intake temps, MPG, knock, etc.) I have ran both a stg1 AP OTS, stg2 OTS, stg2 protune (via AP) and now my 20G on my AP. I was fortunate to have Tim Bailey tune my car, he did wonders with it. I have about 10-12 different maps, both 91 and 92OCT limp maps to 20PSI maps. The AP isnt for everyone, its not as cheap, some say its not as easy to use. When I got my AP I had the car for only a few months and was on the waiting list for Cobb to ok the AP for the 07. I have yet to have any issues (in 5yrs) that were not resolved quickly with the AP by either Cobb or my old tuner shop. Just talk to your tuner or a tuner you trust and knows these cars, read and research and see what fits you and your wallet.
"2007 WRX- PPG'd, 20G- Tim Bailey tuned
Stage 2 2005 WRX