Wound ballistics and stopping power of calibers are still debated even by the experts. But the only real guaranteed measure of man-stopping power is the size of the wound channel the bad guy is going to bleed into. Unless you hit the central nervous system they're not sure to go down straightaway, and that's not very likely to happen. I had a friend a number of years ago who was attacked at several feet by a butcher-knife wielding assaillant while responding to a routine call. The first round (38 special +P hollowpoint, in performance very close to a 9mm Hydrashock, these were the revolver days) went dead center into the guy's chest. He kept coming and managed to put a slash across the officer's face, friend still has the scar. The second round went through the bad guy's cervical spine, and the assailant collapsed immediately, effect described as being like a switch turned off.

No normal pistol round is going to have enough energy to physically knock someone down, they're going to hopefully fall down from shock and pain, and years of self-visualization from TV and movies that that is what one does when one gets shot. The problem is with the bad guy who doesn't realize its time to fall down. In the 1986 Miami shootout between the FBI and the two armored car robbers, which left two agents dead and around a half dozen more wounded, one of the suspects fought for several minutes after sustaining a 'non-survivable' wound to his aorta.

I think a 9mm hollowpoint is a good round, its what I carry off-duty in a Browning BDM. I would not go any smaller though. The 40 S/W (10mm short) is a bit more powerful. The 10mm and 45ACP are still the kings in my eyes. The FBI's research shows the 10mm might be just a tad better man stopper than the 45. But they'll all work. I think its what you're comfortable with recoil-wise, and what you can afford to practice with! All the foot-lbs. in the world aren't going to save you if they're zinging over the bad guy's shoulder. I don't know about down under, but in the states 45ACP is almost twice as expensive as 9mm. I also like the nine because I can carry sixteen rounds in an off-duty capacity in a slim pistol, where I might not have a spare mag around.

As far as brand name guns I like dependable ones, Brownings, Rugers, Smith revolvers, 3rd generation Smith autos. I personally have had a lot of problems with Berettas and some with Sigs. Never shot a CZ but I'd like to. Glock is a good combat gun but you need to be damned careful with it, 4.5 lb standard trigger pull isn't much.

All just my two cents anyway