There are many ways to improve the stock suspension.

1)  Adding different tires- stiffer sidewalls
2)  Add different springs
3)  Add different shocks- lower/raise ride height, increased spring rate�
4)  Add different springs and different shocks
5)  Add a bigger front sway bar with rubber bushings
6)  Add a bigger front sway bar with urethane bushings
7)  Add a bigger front sway bar AND add a rear sway bar with rubber bushings
8)  Add a bigger front sway bar AND add a rear sway bar with rub urethane bushings
9)  Add bigger front sway bar; add a rear sway bar with either rubber or urethane bushings, different springs or different shocks.
10) Adding air shocks to none or any of the above.
11) Adding 15� Rims and lower profile tires

What your budget and desired results.

Springs: @$289 H7R others $???
Sway bar $119 Front/rear w/ rubber bushings
Sway bar $159 Front/rear w/ urethane bushings
Shocks from $29 to over $100 each depending on brand.
Tires $???

Changing the suspension can be costly.  

Adding a rear sway bar helps in controlling the rear end during cornering and cross-winds, BUT only add a rear IF the front bar is increased! Otherwise it will make the car front end unstable and cause steering problems and loss of control!

Robert