if you have a .270wsm and want an all around? personally I see no need for a .270win or .30-06, or .308?

the .243wssm and .270wsm covers everything pretty well up to elk and can still do the job, so the next step up is something like .300win mag or bigger IMO, and if you're saying you mostly just hunt whitetails, just use that .270wsm or .243wssm...

I mean you can double up, but with only 2 rifles I see no need to already be doubling up, but if you really never plan to shoot anything of elk size or bigger I don't really see a need for you to have a .300winmag or larger either.

a 7mm Rem. Mag. might be the cartridge you're looking for though, plenty popular, ammo available, flat shooting, still small enough for deer etc..., though could do the job on big elk etc...though I almost feel like you're doubling up on that .270wsm...

a .338 win mag might be a good option if you wanted to add to your arsenal and kinda cover that next level above your .270wsm.

If you're really against getting a magnum but want a good all around, I think a .30-06 can get it all done for ya, with 180grs it can take the big stuff and do a decent job at it, or a deer with 150/165grs., I'd pick one of those 3.(7mm rem mag, .338win mag, 30-06)

Personally I'd keep what I had, and not double up.