There will of course be those who disagree with me, but many breeds have their own terminal/growth bloodlines available. I say choose your favorite breed combos, and choose a terminal/growth sire within the breed you want to use. Just make sure your cows can handle his calves. Within the Hereford breed for instance, Remitall advertises multiple 900# and up 205 day weights, and they've even promoted at least one with a 205 of 1,000# plus. I think he had a 107# BW...
These weights may well have been achieved with creep feeding, and probably cows that weighed 1,500 and up. I'm not advocating any of these practices, just saying what's out there. I've personally owned a bull in the past that had a spread from 70# BW to 804# 205 day without creep, and he did it in a moderate frame, I'd guess him at about a ton now. He's been breeding a herd of Charolais cows the last few years, and they basically eliminated their calving troubles and increased their weaning weights versus their old Char bull.
The easiest way to get there is some heavy milking cows bred to a growthy bull. Those type of cows also typically require more acres per cow to sustain their production, so whether you are actually selling more pounds of beef per acre is something to investigate. Plus, typically the heavier a calf, the less he brings per pound. Having said that, most of us are trying to develop that easy-keeping AND heavy milking cow, but it is easier said than done.
Good luck