Heavier bullets do better with sub-sonic loads on big game.
123 grains x 1000 fps = 273 ft. lbs.
208 grains x 1000 fps = 462 ft. lbs.
You could, of course load that 123 SST to 2200 fps and have a real sweet bullet for big game with more range but it wouldn't be subsonic of course. Post up what kind of trajectory you get though I've always wanted to know from someone firsthand about that kind of set up.