Officially the RS4 in Europe was 1655kgs (I can't show link as it's now out of production) and the S5's official weight is 1630kgs.
http://ak4-uk.audi.co.uk/sat.do?mand...ories_details=
That is only 25kgs of difference, so unless the US cars are totally different in spec I can't believe it will weigh as much as you and Edmunds are saying.
Now can we discuss your other inaccuracies like the S5 having shorter gearing. You should away check all information before posting and the logical place to start is on an Audi web site.
