check tirerack.com for 19" wheels for your car, and look through what they sell to get specifics on offset & bolt pattern (presumably, backspacing would not be a problem); Then find the specs on the wheels you want to install - if the offset matches (or is close), and the bolt pattern is the same (presumably it would be), then you might be good to go. I don't really know why you'd want to run a larger diameter wheel though - Unless you really like the M3 wheels, if you could fit the same width tires as the 19" M3 wheels on 18" wheels as wide as the M3 wheels, (assuming you can find 18" wheels you like), then you'd save some unsprung weight (19" wheels are likely to weigh more than 18" wheels, generally), keep the car's center of gravity lower, and keep your acceleration by not effectively changing your rear axle ratio. Regardless, if you dig around the tirerack.com site seeing what wheels it shows for both cars in the sizes you're interested in, presumably you'll find the specs to answer your question.
