Personally I would forget about a center until you can afford the sopra center channel which is $3500. I would run a phantom setup which would be 4.1 am instead of 5.1. Your Sopra 3’s should be move than enough to make it work. Anything less than a timber matched center is going to ruin the home theater experience and is why I suggest a phantom center channel. Good luck
Dave-t
https://www.focal.com/en/home-audio/high-fidelity-speakers/sopra/center-speakers/sopra-center