ORIGINAL: ColoradoElk
Although not a "big bore", look at the 30-378 Wby. 3,400 fps with a 180 gr Accubond isn't cheap though, $5/shot with factory loads. Assuming the manufacturer information is correct, that puts the Wby about 450 fps and 1,100+ ft/lbs ahead of the WSM with the same bullet.
Yep, I forgot about the Weatherby Mags, they're unbelievable in performance.