the BMW PE for the 128i is just a muffler, probably overpriced, but I've really enjoyed it. I installed myself, and isn't too bad. No welding is required, there's a decent DIY on this forum.
The sound isn't too aggressive, but not soft either, really think the PE should come with sports package.
2010 128i manual, sport package, performance exhaust, Vorshlag camber plates, 245/45/17 ZII square on et 40 with rolled rear fenders.