Go with the Remington RUM, if the other two do not shoot, your pretty much screwed as far as rebuilding. Can be done but the outcome can be tricky compared to rebuilding a Remington 700.
Plus, in a 26" barrel length, the 30-378 will not outperform the 300 RUM by ALOT if loaded to the same pressures. But you will pay through the nose for extremely expensive brass that really is not the best quality as far as strength goes. Plus, your burning about 15 grains more powder for 50 fps more velocity.
I would not look at the Browning, just to many issues lately with Browning rifles to recommend, stick with the Rem.
Better yet, if you can afford it, start custom from the ground up. May surprise you what it would cost for a full custom rifle
on a budget.