I've read that Injen doesn't perform well when it gets hot. I've also read that aFe doesn't perform well, period -- it actually DECREASES performance.
Based on what I've seen around the forum, it seems BMW Performance is the best option for performance gains. Stock intake + charcoal filter cut out + drop-in filter is the second best option.
As for sound, see SuperAwesome's suggestions...
But seriously, Injen and aFe might sound louder, but they're not the best for your car.