A "case" (to me means 1,000 rds) of duty/defensive .45 will probably run you $500-700 these days depending on what flavor you choose. I would research which loads meet FBI terminal ballistics specs (DocGKR would be a good start), pick a box of a couple offerings from there and test them in your guns for reliability, then of those choose the most affordable load you can get. I am a Gold Dot and HST man myself as they are both proven loads and function reliably in the three .45s I have, however they can get pricey.
On the subject of stacking ammo deep, I personally only stack a few hundred rounds (maybe enough for three or so duty loadouts) of duty/defensive pistol ammo in my chosen calibers (9mm, .45, and .38) but I absolutely hoard multiple cases of FMJ. My reasoning is that: 1. when I train/practice, I blow through the FMJ so I need to keep more of it on hand, 2. in any general lawful defensive shooting, I do not foresee depleting my duty/defensive pistol ammo in any appreciable sense, 3. In whatever fantasy EOTWAWKI/WROL/SHTF/Zombie Apocalypse scenario you dream up...it's probably not going to matter what ammo you hoarded; ball vs JHP.