Just because you have now decided to go beyond stage 2 does not mean that the AP is useless. I run a 20G on my 07 with multiple maps to choose from (12 to be exact). Its much easier and convinient to have the AP in the car over a laptop to log and switch maps. If I throw a CEL while driving I can stop and check it out without having to worry about limping the car back home to check it out. Yes the AP is expensive, but I have got my money and then some out of it. Just my two cents.
"2007 WRX- PPG'd, 20G- Tim Bailey tuned
Stage 2 2005 WRX