I just ordered an AA exhaust and AA pulley that you will be able to hear once I receive and install. I chose the AA because it has the most substantial dyno gains Ive seen and Im a performance first sound second type of guy. Plus I plan on driving to TO in april for the AA software .
Another reason I chose the AA is because it seems to be the most quiet exhaust which is what I need since the X-Pipe I plan on putting on later will amplify an already very loud exhaust (had I chose one that is loud). AA x-pipe with software and AA exhaust is already dyno'd with significant gains where I eventually plan on going later this summer.
Of the 2 you mentionned I would chose the Eisenmann and they now have made connecting pipes so its a true bolt on like the AA. The Remus supposedly has a bad drone at highway cruising speed of about 120 to 130 klicks.
Whatever you decide on I definately would love to hear it since not many in canada/montreal do mods on their M3's. "Slammed" in Toronto has the most from what Ive seen .