I am considering the same thing. Well, not entirely, but the most part. I'm considering selling my Tamron 17-50, even though it is one HECK of a lens. I have the Sigma 24-60 f/2.8 as well, and it's almost (but not quite) as sharp, and has better bokeh. For a lens that I don't use that often, it seems more logical to pocket the money. I'm still on the fence about that, but I find myself using my manual focus primes most of the time in that range, rather than the 17-50. I'll keep the 24-60 so I have autofocus in that range if I need it, but I'll mostly use my primes.