I went from a Canon SLR to a Leica. I really liked everything about the Canon (a 1V) except for the size. Yeah, the Leica lenses are for the most part better than the Canon lenses I used (50/1.4 and 28/1.8). They are also way more expensive. For the most part, the Canon lenses weren't 'bad' and were good enough for most pictures I take. I've thought about going back to the Canon set up and buying some nicer lenses, but after borrowing a 24 L and using it for a bit, I reached the same conclusion - it's just too big for me. I wouldn't carry and thus I'd not take pictures. I travel a fair bit and having a smaller set up is a HUGE thing for me. Plus, over the years, I've gotten a couple lenses that I really like, so the Leica kit is working for me. Lastly, I've found that rangefinder focusing suits me reasonably well, and I don't really miss macro, big telephotos, or zooms.

I play around shooting street but suck at it. The Leica is better than the Canon here, but not because it's a Leica. In my mind, mainly because it's manual focus and it's real easy to zone focus it. So any manual focus SLR would be just as good.

If I were you, I'd look into picking up a manual focus Nikon SLR. There's a ton of glass out there that you could use, including some of the nice new Zeiss ZF stuff, and you could use it on your F6 too. Even if you really splurged, you can get an FM3A for about half of what a Leica costs, never mind the lens prices. You get a smaller camera and manual focus, without the huge price increase or the loss of certain SLR capabilities, like macro.

On the other hand, if you want to shoot a rangefinder and know what you are getting into, Leica's are great cameras and there's a ton of cool lenses out there.

Finally, even though I shoot Leica and Canon, I've thought about selling it all for an FM3A, an F6, and a D700. It's a really nice system with some really nice lenses.