.257 Weatherby is grossly overbore, and burns throats faster than nearly anything else you can find. It is also viciously loud- louder than my .375 H&H to my ear.
Marlin today is a complete don't-do-it under Remington's ownership, the quality has dropped to pretty sad levels.
The Winchester you'd be impressed with, great action, great quality, great value. The .270 is way too close to a .30 cal though in my opinion if you're looking for an in between. .243 Model 70? That's far more of an in between, good varminter, way, way more gun than your .223 with bullets up to 105gr, easy to obtain ammo, and even an acceptable deer rifle. Another great in between would be .257 Roberts, but not currently available in the M70 FW to my knowledge (may be wrong).