i agree a plasma cutter is prob the best option if you have access.
another alternative is a standard circular saw like this:
with an abrasive blade for metal. you can buy a few from home depot or about any hardware. I also like small cut-off wheels for the angle grinder, but the circular saw does a great job at making straight cuts. Sawz-all will do the trick, but again it's difficult to cut straight.
i'm not a safety nut, but you'll want safety glasses and ear protection.