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.