Re: Please help me decide
I'd go with the friends Sendero. You have everything you need to get started, now, with no waiting on parts/service. You can shoot the Sendero/7RUM until the barrel goes. You can load the RUM down to match what the 6.5WSM would deliver, or rev it up and flex your muscle.
You can still get the 28" Pac-Nor barrel at a later date. You'll have a trued action with an aftermarket trigger, setting in a great foundation (HS Precision stock). If you explain to Pac-Nor that you have a muzzle break (MB) you want to use, I'm pretty sure they could contour and thread the new barrel to match the current RUM barrel. Don't know why you couldn't send a .264" diameter bullet through a MB designed for a .284" bullet.
Not sure what the 6.5WSM is capable of, but should be a decent round. I have a .270WSM (24" barrel) and it's impressive! I saw a guy out in Wa. state (RattleSnake Rifle Range) shooting a 6.5WSM at the 1K range and while he wasn't "shutting" everyone down, he was holding his own. Not sure how this round would compare to the .264WinMag. I've always thought that would be an excellent round for LR deer/elk with the right bullets. JohnnyK.