I have never had the Sopras, though I thought about getting some to try. I do know that they use a lot of the technology found in the Utopia line, including the tweeter. I would imagine them to be much like the older Electra line that I loved so much and brought me to the Utopias. I have never been disappointed in Focal, but without having heard them first hand, I couldn't give you a whole lot of other details.
What I will say is that you shouldn't need to concern yourself too much with the lowest end presentation of the speakers in conjunction with the JL Audio. I would think that a crossover somewhere in the 60Hz range should support these speakers and sub nearly perfectly!
Nice system and setup by the way! Let me know if you ever get your hands on the Focals and what you think!