At my last house I used REW to tune my sub. It was flatter in Max Extension, in that room. I brought it to the new house and haven't run REW yet, it seems to sound fine the way it is, and I don't really have much choice in where to put the sub. I do still plan on doing it though, because when I ran it last time, I noticed that even 4" movements could greatly alter the sound characteristics of the sub.
All that said, I have changed mine from ME to MO. While watching "The Innkeepers", there were some very VERY low passages with high output, and I could easily hear port noise. Unplugging the second port remedied the situation. I should mention I watch movies at theater volume levels, so high output is important to me.