I've been struggling with what all of our options are so far for aftermarket exhausts. I have taken the liberty to consolidate it here. If I am missing any, please post below and I will include it in this post. Since some of these exhausts have multiple options I left prices out. I can include later if people are really interested.
In alphabetical order:
Active Autowerk M2 Competition Exhaust (can be paired with separate midpipe, single path)
Link to Product
AFE Power M2 Competition Exhaust (catback, single path)
Link to Product
Akrapovic (can buy just axleback or catback (basically axleback plus their midpipe, dual path)
Link to Product
Eisenmann M2 Competition Exhaust (both catback (race version) and axleback, dual path)
Link to Product
Lightweight (both catback and axleback, dual path)
Link to Product
GT2 Meisterschaft
Link to Product
Miltek M2 Competition Exhaust (has both full and axleback options)
Link to Product
Supersprint M2 Competition Exhaust (all options, dual path)
Link to Product
Remus M2 Competition Exhaust (seems to only be axleback? dual path)
Link to Product