I used to work for a dealer selling Thiel's the subwoofer is extremely good but it is very expensive if you have to add the integrator.
So my question would be do you have CS 7.2? or are you thinking of getting them with the sub?
I use the SS2 connected via passive crossover with the CS6s. The combination is perfect even though it took some time to position the speakers and adjust the sub in my listening room in the house I've been in for a little under a year now. I imagine the combination of 7.2 and SS4 will be nothing short of spectacular and, from my point of view, I don't see any reason why you would need the active crossover unit. Plus, there will be less electronic noise with the passive unit.
"I am using five CS7.2 for multichannel music (SACD)." Luck you! Please let us know what the rest of your system consists of. I haven't heard what your describing, but, I would imagine the sealed box subs (especialy with the active cross-overs) would cetainly be an improvement over the 7.2's passive radiators.