I do believe the GXP does have larger/thicker front and rear sway bars. You can also get adjustable front sway bar end links, but being a front wheel drive car you'll actually see more improvement in cornering with an upgraded rear sway bar, unfortunately there are no aftermarket bars, but I know racingline is in the process of making a set so maybe soon!
I'm sure the GXP also has stiffer springs, no idea about the shocks though.
Eibach makes a pro kit for the G6, it's a middle ground lowering kit that brings the car down about 1.5" but still preserves the quality of the ride pretty well. That runs about $250
H&R also make a set of springs that lowers the car, but not as much as the eibach kit, therefore it's a better ride but not as low. That runs about $230
Each kit comes with all four springs. You can use the stock shocks that are in the car now, or replace them with OEM shocks. You could also try and find shortened shocks that are designed for lowered cars, but I'm not sure if a set is available for the G6...
I personally went with SSC springs (also sold by Canuck Motorsports) and that lowered my G6 about 2" all around, The ride is stiffer but it's actually not that bad. I left my stock shocks in and from what I can tell they all still seem to be in good shape.
Alignment didn't raise any issues, Except the rear wheels are -0.5 degrees out on camber, But it's such a tiny amount that there will likely be no abnormal tire wear.
Hope some of this info helped!
Tirerack.com sells lowering springs for the G6. you can also check ebay, possibly amazon, or did a web search you may find other suppliers.
Last edited by CruisinG6; 07-14-2012 at 02:23 AM.