If only those lenses sizes could stay with a consistent number! I think what you are saying about waiting makes the most sense. Better than making an expensive purchase and regretting it. I can be a little more patient and put the money away for this.

My 70-300 f/4 is a L lens. It works surprisingly very well with the 5D3. (as does the 24-105)

I also have a wide angle lens on my wish list... if I go with the 17-40, it has a 77mm filter size, then I can use filters compatible with the 24-105. If I go with the 16-35 II it has an 82mm filter size that matches the 24-70 II. ernie meenie miney mo. You're right, I really do need to play with the 24-70 and see first.

I have not seriously considered the Tamron... Im starting to read more and more that the IQ is giving the big boys a run for their money...