I have a large enough downpayment to get either one of these cars . The 08 grand prix gxp has pretty low miles at 60k and they want 13k for it. There is also an 09 g8 gt for sale in my area for 12k with 169k miles.The g8 gt is at like one of those small side dealers and the gxp is at a major dealer.I was able to look the g8 history up in carfax. Seems like it had regular oil changes etc. The gp gxp on the other hand had very little history and has only had 1 owner. I'm kinda leaning towards the g8 even though it has much higher miles. If I could talk them down price what do you think would be a fair offer?