I believe the 2008 was the first year of the aux input in the stereo. Not sure if that is important to you or not. Also, there have been alot of issues on here with the 6 cd changer. So I would go with the single cd stereo. Also, the panoramic sunroof has had leak problems reported on here. So the single pane sunroof or none at all would be better. Personally, I wish I would have gotten one with the rear spoiler. 2009.5 has a cool front end and different rear spoiler then the rest, but the fog lights are halogen housing, and not projectors like the older models. 2008 or 2009 GTP is what I feel is pretty much the best package. Then again, that's just my opinion.
08 G6 GT
Modifications: Spyders, HID's Lows/Fogs