one of the main benefits of using a rangefinder over an slr is being able to see whats happening outside of your focal frame lines without panning the camera. So if you are shooting mainly wide open, you're probably taking a lot of photos knowing exactly what you want in your frame before even bringing the camera to your eye. Like Tim already mentioned you might not see much difference in a lot of your shots even if you did buy a $4k 50mm Summilux or a $5k 35mm Summilux. Rangefinders are typically smaller and lighter for the same set-up so it could help with the low-light conditions in which you shoot, but switching for lenses alone might not be the best choice.