If you want the most power you can get from a factory-standard caliber in a service-sized automatic, get a 10mm.
There are wildcats out there that are more powerful, but ammo for them is made by all of 1-2 companies. 10mm ammo is made by CCI, Cor-Bon, Federal, Georgia Arms, Hornady, Pro Load, Triton, Winchester... and so on to the tune of about 15 stout self-defense and hunting loads and who knows how many cheapo practice rounds and "FBI-lite" subsonic JHPs. Order your practice ammo from
http://www.ammoman.com and you will probalby pay less than guys are paying for .45 ACP at the corner store.
"I can`t help but notice that the ballistics of even the hottest loads are just barely,if any, hotter than .45ACP +Ps."
Wrong. In decent bullet weights (i.e. not 165gr ultralights) .45 ACP +P maxes out at around 520 ft-lbs (advertised). All of the following FACTORY loads are more powerful, some by as many as 100 ft-lbs or more.
Cor-Bon
135gr@1400 FPS / 585 ft-lbs
150gr@1325 FPS / 582 ft-lbs
180gr@1320 FPS / 694 ft-lbs (chrono'd from a 6" barrel at 1400+ FPS / 800+ ft-lbs)
200gr@1200 FPS / 637 ft-lbs
Federal
155gr@1330 FPS / 606 ft-lbs
Georgia Arms
155gr@1375 FPS / 648 ft-lbs (Chrono'd from 6" barrel at 1538 FPS/800+ ft-lbs)
Pro Load
135gr@1440 FPS / 619 ft-lbs
155gr@1350 FPS / 627 ft-lbs
Triton
155gr Quik-Shok @ 1400 FPS / 674 ft-lbs
Winchester
175gr@1290 FPS / 649 ft-lbs
No .45 ACP +P load can hope to break 600 ft-lbs, and only one loading makes more than 550 ft-lbs (Cor-Bon and Triton's 165gr +P @ 1250 FPS/570 ft-lbs). "Moderate" 10mm loads operate at the TOP of the .45 ACP +P power envelope (e.g. 180gr Georgia Arms, Hornady & Pro Load @ ~1200 FPS/550 ft-lbs, 165gr Cor-Bon @ 1250 FPS/570 ft-lbs) and go UP from there. With longer barrels, the gulf just gets bigger...
It gets even worse if you compare bullets of comparable sectional density (different-caliber bullets with similar SD will have similar penetration)...
Cor-Bon 230gr .45 ACP +P = 950 FPS / 459 ft-lbs
Winchester Silvertip 175gr 10mm = 1290 FPS / 649 ft-lbs
Cor-Bon 200gr .45 ACP +P = 1050 FPS / 487 ft-lbs
Georgia Arms 155gr 10mm = 1375 FPS / 648 ft-lbs
Cor-Bon 165gr .45 ACP +P = 1250 FPS / 570 ft-lbs
Pro Load 135gr 10mm = 1440 FPS / 619 ft-lbs
C.B.