I have the original RF7's and the Synergy Sub 12.
Despite what a lot of people peat and repeat, the Sub12 is a nice sub.
It doesn't have to do a lot of work if your RF7's have good watts pushing them.
After 2 or more years of playing with adjustments, I settled on crossover around 50,
and my RF7.s on Large for stereo, and Normal for Cinema. The RF'7's can handle down to 34, and I think the II's are rated to 32.
The Sub12 handles the rest down to 27/24. My settings make the transition seamless in my room.
I can't tell the sub 12 is on, except when it is off. Does that make sense?
I also have it isolated from my floor on a marble slab.