When upgrading your car's suspension, it is important to remember that you're going to be the person doing the driving and will have to deal with the ride quality on a daily basis. Whether it is MINI Cooper Suspension, Corvette Suspension, Mustang Suspension or WRX Suspension there is usually a trade-off in ride quality for performance.
Personally when I upgraded the suspension on my 2005 Saab 9-2X Aero (essentially a WRX) I wanted a good balance of ride quality and improved handling. I used the H&R Sport Springs which gave an excellent improvement in cornering and steering response and a more aggressive look, but still retained a decent ride quality. It lowered the car slightly more then an inch in my case which was just perfect for me. Many people go more aggressive, but remember you're driving down the road casually much more often then when your cornering and will have to deal with the ride quality on a permamenent basis.