Lots of swaps have been done, 30-40 by now it seems. $8-12k parts and labor. Can withstand more power, easier to fix/work on. Search 6-speed or manual swap using Google and site:rs6.com. Sure others will chime in, I really like to drive paddle shifting autos myself, so nice in traffic and plenty sporty.

Needed; manual trans, clutch, adapter kit from SteveKen or cobble your own, custom tune from AMD or EPL, bit of interior work around shifter.