I know this wasn't addressed to me- but
Generally, when people are looking at maximum firepower, you end up rapidly reaching the very real limits of handguns.
In general I prefer to avoid a need for firepower, but once you start looking at it, you run into very real facts like muzzle energy, range, sight radius.
I tend to think that firepower is the least important facet of the whole equation- that being said, I DO think it's important, but once you get into the idea of shooting people, you start looking at escalation. It's gonna get unrealistic fast, unless you have a company sized group of trained people moving to a definite location. Which is... unrealistic.
The goal here is closer to what you'd term infirltration or exfiltration, not confrontation. Having a firearm is being prepared, but having to use it means you've failed. May not be your fault, but it's a failure in the mission.
If it's just me and my pistol, that means my family is gone. I might not care about it in that case.