I personally prefer coilovers (I did some autocross back in the day). There is one here and here, but I have no idea about quality.
If you don't need the adjustability (haven't seen a CX9 track car, but I suppose it can happen?), then just the lowering springs will suffice. I'm not sure about the CorkSport springs, but if they don't match OEM specs, your factory struts will likely wear out faster.