Guys, I have tried so many different ways, with and without my minidsp HD, AVR, app, app+Ratbuddyssey, RS spl meter etc., in the end, the best)flatest curve was obtainable by simply running Audyssey, following instructions to the letter, then use the App to fine tune and develop the flatest possible curve using Ratbuddyssey.
Spl meters are not as accurate for setting sub levels as Audyssey (according to Audyssey, I believe them because their explanation makes sense to me). minidsp/REW to time align subs manually is unnecessary except in certain situations.
If you guys must go down that rabbit hole of trying all the things I have, and some, have fun. If you just want to save time fooling around, trust Audyssey a little more, I have documented the steps I took to get within +/- 1 to 2 dB 20-120 Hz. I have yet to see better results posted except Pogre and Jon AA's. If you just follow the steps, it should take only a couple hours, and you will be able to enjoy near flat bass response, or shape you own target curve to the popular one found by Harman.
Audyssey is far from perfect, nothing is, but while Dirac Live may be better overall, Audyssey does work quite well if you limit the upper freq limit to around 300 Hz and follow their instructions, but do use the App.
The KISS principle seems applicable to room EQ for bass too.