Go get a cole hersey 24117 relay from any parts place. It's a constant duty relay and is rated at 65 amps and can handle up to a 4 gauge wire easily (maybe more, never tried, mine's 4 gauge). You can control this from a switch on the dash and shut down absolutely everything. Set your pc for "start on power" (or whatever it is) in the bios. You will need another switch on the dash to shut down the pc before the inverter (computers don't like the power just disappearing while the OS is running).
Better yet, one button on the dash to turn the PC on and off, and wire the CH24117 relay to Acc power. That way the inverter goes on and off with the key and the pc when you chose by the switch.
Here's a setup I'm using (a little different now, but you get the idea). If nothing else, it should get you started if you want to use an inverter and no ssc (I'm using a DSSC soon):
I really would recommend a ssc though. I thought I wouldn't want one either until I incorporated one. I can't live without it now (but I still have a switch to turn it off if I want).