The CC2 center does not play below 160hz, and sounds really bad xovered right to a sub at so high a freq. However it does sound great xovered to the mains.
The mains go down to about 27hz on thier own, but they are tri amped w/ a external xover, w/ a pair of HSU TN1220s at 45hz. Right now, I use the ICBM magnapan version (doubles the xover freq for the center) set at 160, though 200 would work as well, in recombine mode. I run the bass signal from my mains xover into the ICBM, as well as center signal. The info above 160 goes to the center, and below gets mixed with the stereo bass info, and appears at the mains bass panel. No center info actually goes to the subs. I have a third sub just for rears and/or LFE.
What I would like is to have the 990 send the center bass to the large mains (I had a sony 90es that would do this), so the ICBM can be removed, and the tube subs will work along with the bass panels of the 20s.
Even better, but not absolutly needed, would be to have the surround/rears xovered to there own sub (at 80 and 100hz), and not go to the mains. Though they certainly would be xovered there as well. Of course now I have a extra unused sub. Hence the need for the 2nd ICBM that I want to remove from the mix.
BTW, I think today is the 19th! (pacing back and forth)