I have the AFE Stg2 intake...got it for a good price. I would try and find one used to save some bucks. There is a few hp more than a panel filter, but mainly there is an improvement of intake growl over just a panel filter.
2013 M3 Coupe-MR/BLK ZCP, ACM test pipes, BPM Stg2 dev. tune and Megan catback, AFE Stg2. with C/F elbow VMRV810 19x10&19X11 275/295 Mich PSS.
Previous rides: 2011 M3 Coupe-MR/Blk
2007 Porsche 997C2S Speed Yellow/Blk sport seats
2004 BMW M3 Imola/Blk