I got to play with one of those earlier in the year. Not real useful, but fun. And unbelievably hot-- you can feel the heat from the flame 50 feet to the side. I mean the heat, on your exposed skin. It's fortunately not so bad behind it, but it is still quite hot. We set some stumps alight trivially with it.
It appears (the owners are engineers) that it's carefully designed so that you cannot easily boost the pressure and thus the range. You'd have to rebuild the whole thing. Obviously, "more power" was our first thought.
I've got one of those industrial-type propane burners that roofers use, with a 20# tank strapped to a hand truck, I use for burning weeds. Last time I was using it, I said to myself, "Self, somebody's burning tires around here!" YEEEEOW! My boot sole was smoking! And that leather stays hot for a while! Had to make a dash for the hose-pipe to cool off my doggie!