I'd like to get an upgraded suspension, with a bit shorter springs for a more aggressive stance...What kits would you guys recommend? Will it cause any problems like rubbing, or decreased turn radius?

You'll be fine with 18's and any springs.. dont worry.

You shouldnt scrape (I have sportlines, aka the lowest of the low) and I dont.

I'd say you should go Pro-Kit (eibach) with Tokico D-Specs and an Adjustable BMR panhard bar (maybe LCA's and sway bars as well)

Its all personal choice really, there is no right or wrong. Thats just my $.02

+1 i got 18's and they are fantastic

Trust ricekiller, i just got my 18's and h and r lowering springs, not on yet but will be this weekend! Ill let you know, but i trusted everyone on here so i know there wont be and trouble with rubbing!