I guess one question that hasn't been asked is " Are you simply looking for pounds throught the austion mart in the fall of are you feeding the calves yourself."
Scott makes a very good point, but another good point is that there are "fast growing sires" in a lot more breeds than Charlais and Angus.
Had a calf two years ago show on his 2 year old 1266 pound momma at Agribition in Regina Saskatchewan. He was just over 10 months old and weighed 1008. Weighed by the show staff mind you. One of those overlooked breeds - Galloway - ;-)