For a standard-pressure factory defense load, the Silvertips are about as good as you are going to get. If you want to get into handloading, you can put a 300 grain hollowpoint at between 850-900 fps and still be under pressure, though "loading up" a standard cartridge should be done by an experienced reloader.
I own six .45 Colt revolvers, two Rugers that I can load up to my hearts content, two SAAs that I will never run anything hotter than cowboy loads, and a Smith and a Taurus that need their own "medium" power loads. I would guess that the Beretta is a pretty exact copy of the SAA, so I wouldn't press the issue. Hell, Lead flat points will put a hurting on someone when they start out at .451 inches.
Not intended as a crtiticism, but where do you find concealment leather for a single-action? How do you carry extra ammo? Are you limited to 5, or does Beretta use a transfer bar system?