Though you don't have XT32, I still like the idea of running Audyssey first, then checking the situation with REW. You can always kill Audyssey if its not helping. (a simple rew sweep before and after audyssey will show whats being done.)
XT32 + the App just gives you beter control... perhaps better algorithms being employed... but the deciding factor for me, with regards to the app, was the curtain you could set to only work on correcting below a certain frequency (usually between 200-300 Hz, called the Schroeder Frequency).
I think Bill's way would work too, but Auudyssey is the wild card and you might find yourself doing all this work in REW/M-DSP that Audyssey changes and you have to tweak again.