I'm embarrassed to say, but I am not sure what year my Impala is. I THINK '06. Anyways, open the front doors. Look on the left and right side of the dash panels. There are TWO fuse panels. One on each side. In general, I think most of the switched fuses are on the left (driver's) side. Open it up, take a DMM with black to ground and red to each fuse and just cut the ignition off and on until you find one that switches with it. You don't have to start the car each time, just flip the ignition into the position right before you start the engine.
Keep in mind, you should NOT run all of these devices right off of this fuse point. You're best bet is to use a good 30A relay or even a solonoid to control voltage to these devices. Just use the switched voltage to engage/disengage the relay.