Try both and see which works better for you.
I would start with good 10" that can go down to ~20hz. What are your candidates?
There are other brands too like JL Audio, Rythmik etc.Yes, Kec carries SVS. PB10 is using a 10” woofer.
Not sure about your budget but I may be able to build you a proper sub if you are open to this option....
What LCR are you using? Can try to adjust the crossover?
Missions LX4 and LXCI ran AccuEq which sets the crossover at exactly the lowest ratings of the Missions. 40 & 80.Moved it up to 60 and 100.😀