My son is turning 6 in May and is starting to do more sports stuff and my daughter is 2 but runs like the devil and I can't keep up with any of them with my 5D. I have a 40D on the way but thats meant to be paired with the Sigma 10-20 for a Real Estate kit, so that leaves me with the primes (which I love) and probably a 70-200L down the road. I would really like to keep my primes so Im thinking I could settle for a 1.3x crop to gain superior AF and metering. What do you all think?