Hi, I just upgraded from the 7D to 7D II, and I am looking at the lenses I want to upgrade next. My most challenging subjects are sports. I use the shorty 40 and nifty 50 for basketball, f/2 100 for volleyball and love my Tamronosaurus Rex 150-600 for football (all small school high school). At least one of the schools I cover has the reputation as the worst lit gym in the state. The Tamron does everything I need for football but I would like to improve my kit for the other sports. I have a personal budget of $500-$1,000 per year for new lenses. I would like to get f/2.8 zooms, covering 24-70 and 70-200 over the next few years. My question is, should I sock my money away and get the Canon L lenses over 4 years or are the Sigma-Tamron-Tokina options good enough for half the price. My top criteria would be auto-focus performance in AI servo mode.