I just pulled the trigger on a 24-105mm Canon L lens. I've been debating to get that or the 24-70mm Canon L but after reading tons of reviews and asking a bunch of people, I just made my purchase. Now, my question is this. I have some cash left to buy myself one more present. I can get a good deal on a Sigma 10-20mm or I can get myself a flash (canon 430ex II speedlight). Which one should I get? The flash will be important for my new lens because it has f/4 aperature and I will be working in some low light conditions. But.... The sigma 10-20 would fill my focal range a bit more. What should I do?