As you move from 6-06 to .280AI, you're going to trade some recoil and barrel life for wind drift and hitting power. You have to decide how much recoil, barrel life, wind drift, and hitting power you want in your rifle, but for me and speed goats, I'd roll with a 6-06 twisted at 1:7.5" running the 115gr Berger VLD or the 105gr Hybrid.
If looking for cheap shooting, then the 105gr Hornady HPBT or A-Max would be swell. Barrel life isn't going to be stellar, but you'll be able to spot your shots when using a heavy rifle, wind drift will be manageable (nearly identical out to 1000 yards using a 105 Hybrid at 3305fps vs a 140 Hybrid at 3000fps from a 6.5-06), and killing power will be plenty.
