You have more overlap than gap. You could go above or below what you have with a 375 H&H or a 22-250 . Or a 243 or a 458. However you mentioned killing deer in the 230 lb class at up to 400 yards. That won't be just any rifle.
If what you really want to do is slip something in between the 300 W Mag and your 7mm/08 then you could certainly consider a 270 or a 30/06 as has already been suggested. But you are really pretty well set for a wide range with the 2 firearms you have.