Using my gorilla math I ran a 2500 watt amp off of a 60amp fuse for 2 years. So I believe you when you say you haven't seen high current numbers.
I've never put a current meter on my equipment but I'm guessing it's generally low.
Truth be told, only a few people that put together large (as in my case, 2000-3000) wattage systems are pulling the numbers that they THINK they will, that justify huge upgrades in the electrical; theoretical is not reality for most. That said, the big three is always a good start but even with the potential draw I COULD see, don’t see the need to install the 250Amp that I have sitting in the wings for the “just in case” scenario. It’s never a bad investment though and I’m sure I will put in at some point, just because I don’t want to keep hearing about it! And as is the case, there’s always that Db drag race at the intersection that one has to be ready for! If I was doing SPL, running everything at 1ohm, sitting around playing for hours at a time, definately.
In the daily driver I have two FOCAL 2300rx’s and a DS18 EXL2500.1 (running all of them at 4ohms) and even at VERY loud volumes never have pulled more than 47amps. And seriously, it’s really loud! If you are drawing current that you can see dim your lights or causing your amp to shut down, that’s usually a pretty good sign that you need to upgrade something. People going to flip me shit for downplaying the need but hey, I say it all the time, opinions are like a$$holes, everyone’s got one!