As Warrior indicated, best-placement predictions from a floor plan are dicey. Traditionally a corner gets the best results, but I’ve occasionally seen situations where it didn’t.
However, I’d suggest that the “bass crawl” technique is old school in this day and age of cheap room measurement software. It sounds like you’re putting some serious money into this set-up, so you might as well go all the way and do it right. I’d suggest spending an extra $100 or so on a calibrated USB mic from Cross Spectrum Labs. Go to Home Theater Shack and download the free Room EQ Wizard software, and then you’ll be able to take frequency response measurement that will enable you to determine the best locations for your subs.
Regards,
Wayne A. Pflughaupt