The Mamiya 7 is wonderful, but the lenses are not fast. I have the Hexar AF and it is nice to use, quiet (sometimes I can't tell that I've taken a picture), and has a great 35mm/2 lens. I don't always remember that it is auto focus and sometimes I miss the subject focus a tad, but I like these cameras. For a rangefinder that is faster to use and has interchangeable lenses, I like the Contax G2 and it is more convenient, cheaper, and as sharp or sharper than a Leica, albeit not as quiet (for that the Hexar). The Contax is AF, too, and not a true rangefinder, although there is the Hexar RF (recently discontinued). I have an M3, but without a meter, it is not that fast and I think that fast is what 35mm is all about. If I've got lots of time for the shot, I use the Mamiya 7 or the Deardorff.
Try them all.