Are you curious whether rangefinders will work for you, or are you pretty sure you want an interchangable lens rangefinder and just want to know which model will work? It sounds like you've been using SLRs pretty exclusively, so you might want to pick up a Canonet and make sure it's for you; I certainly found the experience of using the Canonet to be vastly different (and superior) than the experience using my Moskva, which is probably why I bought a gigantic Fuji the other week.
One positive thing about trying the Canonet first is that they are not bad cameras in their own right (very light, small, quiet, speedy) meaning it's not like it's a waste of money, and as well they aren't particularly expensive so if you find out it's not for you, no real harm.
If you want to know which interchangable lens rangefinder is a good idea, then you seem to have the right idea as far as I can tell. I am happy with my GL690 but that is not for everybody and finding lenses for it is like finding hen's teeth anyway.