Why don’t you use the 6.5 PRC on a bunch of deer/elk, and then after you’ve got a better handle on what sort of results you can expect with it, you can decide what to do with the .300. I have a feeling it’ll become clear to you after you’ve shot a bunch of critters with both.
^ My thoughts too, the OP already has a 6.5 PRC, might as well give it a try and see whether he's satisfied with the performance on elk, if so ditch the .300. I don't shoot animals very far out, but I have killed two elk with a 6.5 CM (127gr LRX and 140gr AB) and one with a .270 (140gr AB) and was satisfied with both. With the right bullet, the PRC should be at least as good of a performer, although personally, I do think I'd try the 142gr ABLR over the 129gr for elk.
If you just really like the .300 WM and don't want to let it go, no reason not to chop it down a little and run .30-06 level loads, they kill very well too. Another option would be picking up a suppressor to use with your cut down .300, the big reduction in recoil and blast make suppressed hunting a lot of fun.
