There is no point in an EQ. The point of an EQ is to set it up then leave it alone. All controls like an EQ that are manditory to setup in a specific install will be setup and NEVER again messed with because there is no reason to.
Just go buy a 20,30,40 band EQ and get an oscilloscope and start tuning the EQ and the amp(s).
If it's ran through the stereo, there would be no reason for you asking so you must be running the whole pc setup as the stereo. If this is true, again, get an oscilloscope and set your amp(s) up. In reality, the volume on the pc should be between 75% - MAX. I have yet to test this yet, but this is theory. Once i get the pc in my project after remodeling some things, i can use an o-scope and see exactly what it needs to be set to.