I just got a soundstream eq. On the box it says input voltage range 2~6 v. My head unit manual says line-out level 1v. Will I still be able to use this eq?
Yes it'll work. No matter what HU you have at it's lowest volume setting it will be putting out less then 1v, as you turn the volume up the voltage will go up. That 2v-6v is probably where there item works best.
It does not require 2 volts minimum. Like said above, any h/u with the volume turned down is capable of outputting less than a volt of signal strength.