Who makes the best exhaust? Sheez....that's so dependent on personal preference that it is about impossible to answer.
I think all of them will prolly net about the same gains, which aint huge. The biggest bang you can get is weight reduction. Some are as heavy as stock, some are much lighter, like the Amuse. Sound is personal preference.
I would say PencilGeek is right on track with the mods. You may also throw in an underdrive pully as well. May help a bit....
If you seriously want to go faster, consider weight reduction! CF trunk, hood, racing seats, remove sound deadening, lighter wheels, etc, etc will yeild acceleration gains too.....
Speed costs money...how fast you wanna go?
Tim <--- apparently likes "3" cars
2014 MB E63S
2008 E90 M3 -- Selling
2004 GT3 -- Sold
1997 M3/4 -- Sold
1995 M3 -- Sold