thanks for your reply I take it the ride quality won’t be the same with 19 inch rims ??
Beyond "won't be the same", I'm going to go with "will not be acceptable." These are highly engineered performance cars, you have to keep in mind. A good rule of thumb with highly engineered performance cars is that they don't perform well with parts that weren't highly engineered specifically for the car -- brakes, tires, wheels, pistons, rods, whatever. You start throwing shit on the car that wasn't designed for it, and you're just asking for trouble. On your boulevard cruiser, maybe that's less of a concern.
And maybe your "show car" comment is instructive here. You don't plan to drive the car the way it was engineered to move. Fine. People here tend to drive these cars the way they were intended, and have generally tested the outer bounds of what works. SL600 Brakes, sure. Euro headlights, sure. LED Depot lights, not so much. 18" wheels, on the border. 19" wheels, out of the question. Chinese Uro parts, no comment. I think that's what people are expressing to you. The 18" wheels from alloywheels.net may give you the look you're going for without setting yourself up for ridicule.
But if you drive it AT ALL with 19" wheels, be prepared for it to feel like shit and for someone to say "take those big ass wheels off and maybe it'll ride better."
Think 21's on an E55...
maw