Autocross to Win (DGs Autocross Secrets) - The Driver
On suspension, bilstein coilovers, the ONLY way to go.
Also ZZP front LCAs, and BMR rear suspension kit + STB's.
All granted it's class legal.
Coilovers will be the best place to start.
But this is all granted you figure out the wheels/tires first. That matters more than suspension.
Your plans for power mods literally won't help you at all if you can't lay any power down.
And seeing as its off road you plan on tackling, forget about it. The stock diff will shear into pieces. It simply does not like the wheels spinning at different speeds.