Your decision to get the 35mm ASPH Lux is a good one! I would add the 24mm ASPH, as it will give you about 32mm equivalent on the M8. That seems like a good idea, since you can shoot both the M8 and M6 in essentially a 35mm focal length by using the 24 on the M8 and the 35 on the M6. I have both these lenses and can recommend them. You can even swap the 24mm onto the M6 when you need the extra coverage.
I seem to like the 75mm focal length on the M6. I use the Summilux. It is however majorly heavy. I don't mind; but if you do, then the new 75/2 Summicron might be a good choice for you, or the new 75mm Summarit. They won't weigh down your kit so much. On the M8, 75mm acts like a 100mm, which seems still in a reasonable range for the rangefinder camera. 135mm seems just too long to me, even on the M6 or M3! When I need a 135, it's time to use an SLR.
So I'm thinking 15-24-35-50-75. How does that sound?
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