Just curious - does your guide know you are planning to bring a 6.5mm PRC? I only ask because some folks have mentioned guides having a 'minimum caliber' restriction on their elk hunts. Some require .270 and above. Others make the cut-off 7mm and up. Probably some even want .30 cal or bigger. I'm not saying you NEED a bigger cartridge. I think your choice will work fine with the right bullet. But wanted to make sure your guide knew what your plan was before you got too far along in the planning/preparation process.
Assuming your guide is 'good' with your choice, you might ask him/her what bullets they 'prefer' you use. The ELD-X bullet has a good SD and BC, but it is not a 'controlled-expansion' bullet. The ELD-M is 'technically' not even a hunting bullet; it was designed for target shooting (not that people haven't used it on game...)
Elk are big, thick, and resistant to death. The 6.5 PRC can do the job and you are smart to seek out bullet recommendations. If you are looking for something that will likely pass all the way through an elk (which is good for blood trail and striking as many structures as you can) you might also consider the Barnes 120 gr TTSX or the Hammer 139 gr "sledge", since you are a reloader.