[Brad the best]

Id use a hole saw , a jigsaw or reciprocating saw . last thing i used was a air grinder with a tungsten carbide bit . they rip through anyhting but you have to be carefull . dremels are week little machines i like the air grinders better . then again i have a 300 gallon compressor . the plasma cutter would just me messy . if you have to a drill and a pair of tin snips would do the job . drill a hole big enogh for the snips and cut away (by the way this is more difficult .then the rest . a basic drill should be able to rip through your case like butter , its what 22 or 20g sheet metal . 14v cordless works . i use the 12 amp 5/8 t-drill for fun thow (not advised) looking at dremels site , i like the diamond disk