The problem with the 205/40/17 is much more complicated than just the ride. The main differences come in for braking and speed engineering. Any time you go above or below 3% of the total stock rim + tire diameter, you are looking for trouble. After doing the calculation, your 205/40/17 tire/rim combo is 4.13% smaller than the factory's 215/50/16, thus putting your car in a whole new world of mechanical changes.
First up is your speedometer. When your speedometer reads 62.5mph, your car is actually going 60. Your revs per mile on the 205/40/17 setup will be 886.9 compared to stock at 850.3 (engine wear & tear and gas mileage =
) About the only thing that will probably improve rather than worsen, is your braking performance, since your brakes will have less rotational area and mass in the 205/40/17 setup to halt.
Nonetheless, the aforementioned should be enough incentive for you to sell those tires and slap 215/45/17's on that baby, shich should even you diameter difference ratio to .61% larger than stock (Well inside the 3% threshhold
)
XL
you could have definatly been able to go with a thicker tires.
, those things are gunna explode when you roll over a quarter, much less a pothole. 
Let the modding begin!