I have a 2005 3.6 which is stock, with the exception of the airbox (k&n cone filter), headers and no cats and 3" borla race mufflers. I'm running a Motec system and was recently dyno tuned on what he called a conservative tune at 270 whp. Car weighs in at about 2530lbs (haven't weighed it recently).
I run 245/40 and 275/40 tires or 250/650 280/680 slicks. I've got aero front and rear, GT3 style front "splitter" - Toth Canards and a rear wing.