I haven't really had any experience with springs other than my SSI's so I couldnt tell ya if the H&R's are the way to go, mine are fine, the main thing is just getting that lower center of gravity and wider tires, even if you still run the 15's they'd help out alot...as for power...Base model cobalt, automatic, naturally aspirated, and fast dont go in the same sentence...
My Naturally Aspirated Automatic Cobalt Sedan is really FAST!!! FAIL!
2008 Black Cobalt LT Sedan - SOLD
2009 Rally Yellow Cobalt SS/TC Coupe - SOLD
2002 Alpine White Impreza WRX - CURRENT