NextGen Vehicle: Police Cruiser

I would model the wheels separatly (bad english I know), so it would be easier with the poly calculations. about the details, for the sirens, if you use straight basic solids like cylinder and sphere, you can get really smooth results with a low polycount, and save those for other details.

Just my 2 cents, because I really don't know about low poly, but that's what i'm using now.