I use the "Flat" option but C-weighted works too.
Looking at your C-weighted graphs, you have strong response down to 40hz in room. So your crossover seems fine.
I think that dip centered around 80hz is what's causing the perceived lack of bass. These types of dips and peaks are very room dependent, and they are ALWAYS present with box speakers. It's just a question of where is the peak/dip and how bad. For example, in my room I have the opposite problem - too much bass in the 70-80hz area.
Try this - put pink noise through your speakers again, and then get up and slowly walk around the room with the FFT program running on you phone/ipod. Do the bass peaks/dips change? You'll probably see that they will. You could move your listening chair forward or backward in the room if you see it fills in at a different location.
The 2nd thing to do - move the speakers closer to the wall, see what that does. And also move the speakers further into the room. See what that does.
As a last resort, you can use an EQ to boost the 80hz region. But only do that if you have a fairly powerful amp, as that will tend to eat up watts.
Also, bass traps can (counterintuitively) help with nulls because they absorb the reinforced bass signal that is causing the cancellation effect. GIK here on AC has some great products for bass traps. But they are big.