Have you checked out ratbudyssey? It'll run on your PC and you can load the .ady file to manipulate the curve at very specific frequencies a lot easier than the app.
It's pretty cool if you need to do some very specific tweaking.
I'm out of town (rebuilding a large sundeck on the Family Cabin - a very slow and laborious process - I'm sore all over
) for another week, so I haven't been tweaking anything but the 5.1 system here. It's not a capable receiver (Sony) to tweak with any App.
I may try ratbudyssey when I get home, but after I try the adjustment via the App on the X4400H. I ran some baseline graphs with REW, and there isn't too much "off" that I can see (other than the limits of my Subs for ultra low Bass.) If I can do some minor things in the App, that'll be about as far as I'll go. But if I don't get the results then perhaps a step up to ratbudyssey would be in order.
Wasn't there some controversy with the creator of ratbudyssey not having any receiver capable of running the App, and subbing out some programming to someone in Russia which went sour? Was that all sorted?