Truth be told, there haven't been many report of antibiotics 6.5CM that would shoot. Spend as much or as little as you like, chances are pretty darn good you end up with a shooter.
P.S. I know a guy that has a cut-rifled 6.5CM with an undersized tenon, screwed and Devconed to a 700 action that shoots really well. That said, seems pretty hard to screw up not get an accurate 6.5CM.