I know there are more detailed articles but I asked a couple of people how to set gains on inuke amps for subs (others as well, i just own inukes) and ltd02 sent me a very logical explanation . I figured I'd make it a thread for others with the same question. Here's the steps :
the quick and dirty way is:
1. DISCONNECT your sub from the amp
2. get a bass heavy movie clip like War of the Worlds, Lone Survivor, Pacific Rim, etc.
3. play the track at full reference -0db on the avr ( make sure your speakers can handle this spl. If they can't turn volume up as high as speakers can play clean)
4. turn the gain on your amp up until the clip light comes on
5. if the clip light DOES NOT come on, increase your subwoofer/lfe trim until it does
6. if it still DOES NOT come on, you need a voltage increaser/bump box
7. if the clip light DOES come on, then your AVR have plenty of voltage the way it is set up
8. turn the amp gain down until the clip light only flickers when the track is played.
9. go back to your avr and turn the volume down
10. reconnect your sub
11. play the track and increase the subwoofer/lfe ON THE AVR if necessary leaving the gain knob on the amp alone
12. if that DOES NOT get you enough bass, then turn up gain on the amp by as little as possible because you will be eating into the amplifiers headroom trading off the possibility of clipping some signals for more spl on average.
Now I am sure something similar has been posted in many threads but its tough sometimes to find. Hope this helps someone.