Aside from already having the magnum action, seems like the 6.5/284 could be Your Ticket to all-around performance with chance for longer barrel life than any magnum affords. Might watch David Tubb's video of The One Mile Shot where he uses 6.5/284 to deliver the goods. Pretty much the optimum performer for balance of velocity and accuracy. Not much more than an optimized 6.5-06, except you get much enhanced magazine load-to length when using long action versus a short-action.
Load using the Sierra Accuracy data for their 142gr MK and then go to work tuning your rifle. Proven does really mean something. Joe Rychetnik touted the .257wby as the all-around Alaskan ctg, except for Big Bears. Not much bullet selection in .25cal though...
I'm not a magnum guy for any caliber under .338; and then I'm not looking to burn throat with anything over 75gr of slow powder. Does the extra flight time @ 2770 fps vs. 3100fps really gain that much advantage on wind drift at 700yds? Does the gain in drop matter that much if you can dial for it with proven confidence? I decided these things were in the realm of angel #s dancing on pin heads; but maybe that's me (insult anticipated).
At some point I lost my thril in the chase for more bullet horsepower. Reliability and longer barrel life were, it seems, the greater quest. I'm happy with the .260rem and a .30-06ai instead of a .300mag. My .338/300win enables 65 to almost 79gr performance range using XMR 4350 with a 250gr bullet. If choosing today, would go with a .338 necked-down .375ruger mag ctg; or at least would study that one intently. Maybe a necked-up .308 Lazzeroni Patriot; but I don't care for the .590 boltface ctgs.
Nice to have magazine capacity gains and better bullet seating options which the .284 case variants enable, plus powder stack improvements. Not a whole lot to brag about to the guys at the range or hunting club, but what works might just be what matters most. Also got that Lapua brass mojo working for you. No barrel burners for me, thank you!