6.5-284 will work very well for you if you know how to reload and hunt
shot placement will do alot for you over just buying a bigger round that will kill your shoulder and burn alot more powder. i have 1 on a rem 700 action and have taken many elk with it. bullets used on elk have been 140 nosler partition,140 barnes x , 140 Aframe, and 130 swift scirocco II
all have been 1 shot kills but none have been 700 yrds running dead away
again shot placement anytime over big caliber
my longest on elk was 548yrds with barnes X that was a clean pass through
good luck and post some pix of your new 6.5-284 if you pick 1 up