The unconventional room shape and use of two subs should really help to keep room modes in check, so you have a good starting point. (Good subs, too.)
You could do the "crawling for bass" thing to determine the best locations. I understand your reluctance, but it only requires moving one sub to the couch.
Blending with your main L and R speakers is considerably easier if the subs are in close proximity to the speakers, so leaving the subs where they are in the layout diagram might work quite well. (That's probably how I would lean, I'm a bit OCD about seamless, perfect sub/mains crossover.)
You could deploy one of the subs behind the couch for that tactile near-field bass, but placement in the middle of the room is generally suboptimal.
