After talking to BrianP over the phone from Sensible Solutions, and getting some feedback on Ethan's forum thread, I ended using OC703 but also used this guide you gave me http://www.radford.edu/~shelm/acoustics/bass-traps.html from Steven Helm.

Brian said I would get much better results using the 703 superchunks compared to mineral wool or even straddling the corners with 4" material. He also gave me suggestions on treating the rest of the room, although I'm going to do a little bit at a time.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85