horsepower to suspension limit

The rear upper shock mounts will not live long with coil overs or air shocks.

If handling is a goal (and it should be) this is the basic order of improvements:

Rebuild entire front end.
GOOD shocks
Front sway bar.
Larger torsion bars
Rear springs that match
chassis stiffening
serious wheel/tire combo
bigger and lighter brakes

The steering gearbox can be changed about anytime. The more you tighten up the rest of the suspension, the more you'll enjoy a firmer box.

Improving the basic factory suspension works quite well for a street/road car with basic upgrades. $1500 should get you big improvement.

If you're made of money, there are complete aftermarket suspensions also.