Hi, my first post to this forum. I have a canon 20D, 50mm 1.8, 24-85mm usm, and 100-300 5.6. I shoot mostly kid portraits. My 24-85 sucks at wide open in low light for sharpness. I was looking to replace this lens with a similar range. I looked into the sigma 24-70 2.8 but got the impression to hold out for the canon L glass. I recently got my first strobe - Alien Bees 800 with giant softbox, and I have a reflector. My 24-85mm performs much better with the stobe at 5.6 vs wide open with window light. So what should I add to my arsonal? I thought of a second strobe, instead, but am leaning towards a new lens tonight. Can only buy one thing for the rest of the year. The lenses I am looking at are the canon 24-70L 2.8 canon 24-105L f4 IS (image stablizer) I was told to go for IS always. But I don't see a 24-70L with IS. Would you rather have the 2.8 or IS? (They are the same price) Thanks!