I faced the same dilemma you are describing a few years back and decided, after a lot of the same research I'm sure you've gone through, to use my SLR for getting out of the fixed-lens-rangfinder box. Not just for wide-angle, but for portrait-length and telephoto options - also for having more options for ASA, shutter speeds, exposure comp and all the other goodies that a nice SLR provides.

I still love, and use frequently, my rangefinders but made the decision not to get into the GAS for M-mount and other collectible lens lines. Not enough bang-for-the buck for as infrequently as I use, say, a 21mm lens. At the price point you mention, you're only scratching the surface of what a versatile interchangeable-lens rangefinder kit is going to cost you eventually, if you're anything like me...