I've heard of whole Akra set up in person, its really nice. Not too loud yet very sporty at the same time. I haven't heard the Eisenmann sport in person yet but I would probably go for the Akra system for the weight savings and performance increase.
'08 E92 ///M3
- AW/BLK/CF, M-DCT, 19's
H&R, Vorsteiner, Eisenmann, BMC, BBS More to come...