JWH, maybe to clarify this a little, the .458 SOCOM is a rather specialized cartridge designed specifically for a lot of power in an AR-15 platform. For this purpose, it DOES provide an exceptional amount of kinetic energy.
Once one moves away from the AR-15 platform, which you seem to intend, the .458 SOCOM offers no special qualities and is easily exceeded by many other more popular (lever
Lever guns are plentiful in other more appropriate calibers, such as those recommended above. I have a.444 Marlin that offers about as much power as a .30-06, and the .450 Marlin offers more power yet:
.30-06: 180 grains/2,700 fps/2,900 ft/lbs.
.444 Marlin: 240/2,350 fps/2,940 ft.lbs.
.458 SOCOM: 300 grains/2,000 fps (claimed)/2,665 ft.lbs.
.45-70: 300 grain/1,800 fps/2,158 ft.lbs.
.450 Marlin: 350 grain/2,100 fps/3,425 ft.lbs.
I say "claimed" with the .458 SOCOM, because that's what the designer's say in their sales hype, but other sources say it's more like 1,750 to 1,800 fps, or, about the same as the .45-70. Even at the claimed 2,000 fps, of comparable lever gun choices, it only actually exceeds the .45-70 . . .
Subsonic? Any of them can be loaded to sub-sonic levels, if you're willing to toss all the above energy out the window. At sub-sonic velocities for any/all of them, bullet weight alone will determine energy, and anything in .458 diameter is going to deliver the same energy with the same weight bullet. If we load a 500 grain bullet at 1,050 in all of them, they all deliver 1,220 ft.lbs. . . .