I don't know if it helps with your decision or not, but it is a really bad time to buy into M-series Leica gear. During the past year or so the prices for 2nd hand Leica cameras and lenses have been going insane (you would definately be buying high).

Would you have to sell your F6 to fund the Leica? If so, I wouldn't do it - why trade in a camera that you really like for a total unknown. At the very least I would look into buying a cheap 2nd hand Cosina voigtlander camera/lens to help you decide if you even like using rangefinders before jumping in with both feet.