You said you hated the Mac, so there's no sense trying to reason with you..... ��
But.... I'd say skip the rangefinder altogether. I wish i had. Would have saved me a ton(ne) of money and an equal amount of frustration. Some people just aren't made for rangefinders. I do recognize the allure, though, and it was strong for me. In the end, though, I really just dislike composing and focusing with those mechanisms. If you like your Pentax, I'd ask just what you think you're missing in the RESULTS. Seems like you feel it's the Leica EXPERIENCE you want, and I get that. You've got x dollars. If you were to buy an M6 or 7 on credit or borrowed funds, you could sell it for the same amount after a year of experimentation. An Ikon, for me, was a better experience than my M7, but I still recognize I had to get the M thing out of my mind to know better. As good as voigtlanders are, they never felt nearly as good as the zeiss or Leica to me. Earlier Ms are beautiful, but for he kind of stuff you want to shoot, do you really want to be guessing at exposures?
Medium format - the Bronica rf645 is quite nice, when it works. Same with a Fuji ga645....
But, I think I'd recommend you stick with a 35mm SLR and add a more 'rangefinder-ish' lens like a 35 or 28mm. Maybe pick up a PENTAX ME Super for a song. Amazing viewfinder.