The 6.5 CM would be more than sufficient for cow elk. A logical step up would be a std .30 such as 308 Win or 30-06, both excellent NA big game chambers. The 30-06 and 7mm Rem Mag are so close in field ability, except 30-06 would provide more punch on very large game with its heavier bullet weights, while the 7mm RM would have advantages with 140-162 grain loadings for prairie game such as pronghorn and mule deer a county away and in any alpine setting where a flat shooting gun can save on hiking a bit further.
