I have the Hexar AF, it is a far different experience from the manual focusing rangefinders as everything is automated. However the autofocusing works on the principle of a rangefinder rather than your standard SLR autofocusing. Ultra silent, and super convenient.. If you want a cheaper M mount option, the Hexar RF offers AE and auto film advance, so its like a Leica M7's cheaper brother.
If I were you, based on the benefit of hindsight, I would get a used leica M2, or related bodies. If you don't like it, you can sell it and you won't lose money, possibly break even. If you do like it, you can take pride in the fact that you have one of the best picture making machines in the RF world. The Leica is built like a Rolls Royce. You wouldn't need to upgrade other than within the M series. Just my 15 cents worth haha