get a .300 WSM instead maybe?
I feel like the 3 rifles/cartridges you currently have are all in the same range of power, the .300 is a step up, though still fairly close to the 7mm RM and .30-06.
If you're really just looking to get a new rifle for no reason, I wonder if you even should in the first place.
I kinda wonder if you should step up to a .338 or maybe even a .375 to get away from being close to those others.
Personally I think I'd get a .300 WSM instead for a .300 win mag, and I already have a .300 win mag that I really like, and still kinda want a .300wsm.
another option is getting a .300 weatherby or .300 RUM
a .338win.mag might be the perfect option though, step up to a .338, still flat enough, but shoot big bullets at big things, can handle anything in NA well. Still great for elk, even deer, hogs etc...great all around.
course while you're thinking about a .338, can get the baddest .338 on the block and get a .340 Weatherby!
and of course a .375h&h is an option...but that's more for bigger than flatter IMO.
My advice would be, if you're set on a .300 win.mag, get a .300WSM.
If you want a .300 but want to separate yourself further from the 7mm and other rifles you currently own, think about a .300Wby or RUM.
If you're open minded, I think a .338win.mag might be the best option.
Get 1 of the following 3; .300 WSM, .338 Win.Mag., .340 Wby.