I have a smaller Bosch 11224VSR SDS rotary hammer that works pretty good for that kind of stuff. It can drill the outline and inner holes for the box location quickly and has enough chipping power with a 3/4" or 1-1/2" chisel to make fairly clean cuts.
If I use anything larger, like an 1-1/2" hammer, I'm asking for trouble, like cracking the mortar joint and popping the whole brick loose.
Although, I have been thinking of trying my big hammer with a heavy-wall core bit to make a hole for a round fixture box at some point.
I also use a 4" angle grinder with the dry-cut blade as mentioned. It does work great cutting brick, but it's kind of hard to use for something like a one-gang box without over cutting the corners.
I've got one of those Rockwell Sonicrafter multi-cutters, but I have never tried to cut brick with it before.
