I think if I had the money to throw at it, I would rather own a .500 S&W lever gun over a pump action any day out of personal preference.
The Big Horn Armory Model 89, if I was going to pay the money for the rifle I would pay for the #1 walnut stock and having it blued.
I have no idea on how well those rounds would cycle. In just about any 300 grain or heavier bullet at standard .500 S&W velocities is going to do the job on whatever you shoot it at.
Expect to pay upwards of a couple thousand or more for this firearm. Expect for there to be a wait to get your firearm.