guf,
I'm going to take a wild guess and state that your Rythmik is probably crossed over at around 50Hz, and probably 24dB/octave since the two response curves you posted are quite similar above 75Hz or so.
Thank you for changing the vertical range although you didn't have to switch it to a 2dB scale, a 5dB scale will suffice given that you are not using smoothing. The horizontal scale needs to be changed so we can actually see frequencies every 10Hz instead of every 50Hz.
Yes, you have SBIR issues. Please read as much as you can about it. It's terribly important imho. I would switch off the Rythmik sub and start moving the Omega's around, while keeping the mic at the listening position or alternatively, move the listening position (i.e. microphone) around. A few inches in front, a few inches back, etc... and see if you can smooth out the area above 100Hz to 300 Hz. You might be able to improve the area from 50-100 Hz as well.
See my other posts for some ideas. And post a few more pictures so we can see the rest of the room. Perhaps there is a better spot for your Omegas.
Best,
Anand.