Stage 2 is all you will ever need on the street.
More is nice but you will never use all those power on the street.
Just wait until you have everything for a stg 3 build and tune it then unless you are sure that just a little bit more from a bigger intercooler is the last and final upgrade you will ever do.
My stock intercooler was fine at I think 17-18psi but then I never really drove it all that hard.
Right now this is all the power you will ever need on the street unless you are into drag racing