You know what... Laser cutting is surprisingly affordable. Rather than sweat in the workshop and potentialy kipper your tools on harder materials, why not look in Yellow Pages and give the local Laser Cutting firm a call? I got a quote this week and was surprised at how affordable it is.
Ironically, with one laser machine they have, they can only cut alloy to 3mm, yet steel to 12mm! It's to do with reflection quality of the metal grain or something.
Treat yerself to a 2/3mm steel panel, powder coated + engraved - nice!
Justin