Okay, "knowing" what I need with a 250EX, I have a good idea, seemingly now,

[performance]

Rambozo,
There are TWO ratings on a torch, AC and DC. The 20 is only 250 amps DC current. AC, on ours, and several others is only 175 amps. That's why. The AC rating on the WP 18 is 250 amps. DC 350.

26 is 250 amps DC, 160 amps AC. 17 is 150 amps DC, 120amps AC. 9 is 125DC, 80 AC (with a lesser 60% duty cycle...others are at 100%.)

[Rambozo]

Fair enough. I know CK rates the same AC or DC and I swear Weldcraft used to, but don't seem to anymore. I probably wouldn't want to push the edge with a Chinese torch either, something I often forget about. I know I have welded hours on end at 300 amps with a 20 plus year old Weldcraft WP-20 on aluminum, but maybe they just don't make them like they used to.

[performance]

You have to remember that inverters can keep things hotter with the faster switching and square wave.