Yes, that's basically it. Send one preamp signal to your amp and another to the sub. Let the sub's built-in crossover, volume, and phase controls (plus its room setup software) do the heavy lifting.
12-18-11: Erictye
Ok this part of wiring is new to me so bear with me. Running full range... that would be running SF and sub out of the back of the C2300 and removing the CBX from the equation. Do I hook up the sub into the output 2? I also just came across some diagrams as well. Or Is this what you mean?
http://www.audioc.com/library1/images/hookup/mhookupe.gif
Your C2300 has multiple outputs, both in single-ended and balanced versions. Run one stereo pair of interconnects directly to your MC2102 amp and another pair directly to your JL F113. When you add a second sub, connect one sub interconnect to each of the subs, using the sub's left channel input for each. The JL is wired so that if you use the left input only it functions as a mono input. It's very simple that way, and you could use balanced interconnects for either or both runs as both your amp and the JL can take either kind.
You must have a beautiful sounding setup. I can't think of a much better combo for musical satisfaction than Sonus Fabers and McIntosh tube electronics.