Well i am not sure if it was an S-430 or an S-500 since it was de-badged, but it did have two shiney chrome exhaust tips, one on either side, i know the amg has daul tips on each side. It was a 2004-2005 model. Anyway i have a 2005 wrx with a short throw shifter and a lightweight pulley. I was following the mercedes onto rt 287 on my way home from work, i was sitting at about 25mph as we merged onto 287 in 2nd gear, the mercedes had an extra passenger and it was de-badged and slightly tinted, i just waited for him to punch and it sure enough he did, i floored it all the way through second, shifted into third and pushed third all the way out then shifted into fourth and we both slowed up at around 95mph. Besides the initial 2 car jump he got on me from him punching it first we stayed dead even. Now if he was going all out or not i don't know for sure, but he was basically going the same speed as i was and i was pushing my wrx as hard as it goes. he did have an extra passenger. So basically 25-95mph Stock WRX vs S class mercedes...dead even, unless he was not trying his hardest.