If you are a GM guy, you will have to have some patience with the XF. With the right mods, your G8 won't stay with it as I have proven on the track before. So that is the kind of quickness you can get to in a roadster or coupe. They have their quirks like any car, but with no help from Chrysler or MB. Your only help will be on here. If you are up to that, then by all means, buy an SRT6. Performance you won't regret. Your wallet will become lighter as you learn the few little additions you can do to make it surpass your G8. Good luck. Anything under $20k with low miles and good condition is a good buy on a roadster.