I hate to tell you this, but your speakers, good as they are, are a bit too small for your room. 18' x 36' is Maxx territory, and would be a stretch for Sasha W/Ps.
The fact that you have a 14dB drop from 1KHz to 200 Hz (upper bass) indicates that it's even a stretch to correct with subs. IME once you have the subs filling in an octave above 100 Hz they start getting directional and it complicates getting a good blend.
I think you're overall on the right track--run your mains full-range and blend the subs in to fill in the bottom octave or two at most. Going up to 200 Hz is filling in almost 2-1/2 octaves, however. You need speakers that can take you flat to at least 100 Hz and preferably 50-60.
However, if you don't want to spend Maxx money, consider Sasha W/Ps and a pair of JL subs, such as two Fathom F113s. They're fast, powerful, clean, and deep enough to add meaningful bottom bass and can play loud enough to fill that rather large space. But I think you need something bigger than the Sophias so you aren't rolling off so high. A pair of 10" woofers isn't much for filling out a 16' x 36' room. A quad of properly loaded 8"'s (Sasha) would do better (plus, of course, a pair of subs).
The fact that you have a 14dB drop from 1KHz to 200 Hz (upper bass) indicates that it's even a stretch to correct with subs. IME once you have the subs filling in an octave above 100 Hz they start getting directional and it complicates getting a good blend.
I think you're overall on the right track--run your mains full-range and blend the subs in to fill in the bottom octave or two at most. Going up to 200 Hz is filling in almost 2-1/2 octaves, however. You need speakers that can take you flat to at least 100 Hz and preferably 50-60.
However, if you don't want to spend Maxx money, consider Sasha W/Ps and a pair of JL subs, such as two Fathom F113s. They're fast, powerful, clean, and deep enough to add meaningful bottom bass and can play loud enough to fill that rather large space. But I think you need something bigger than the Sophias so you aren't rolling off so high. A pair of 10" woofers isn't much for filling out a 16' x 36' room. A quad of properly loaded 8"'s (Sasha) would do better (plus, of course, a pair of subs).