System Installed, Now how to set the gain?
 

My amp is finally installed, but I'm not really impressed with the sound. My speakers are rated at 90 watts but it doesn't even seem close to that. When I turn the volume up I notice that the clip meter on my infinity amp starts to blink. Is there something I need to to set? also, what settings on the headunit should I be using? Right now the "Loud" setting is on 'Low", whereas before it used to be at "Mid". When I changed it back to "Mid" it sounded like my sub was bottoming out.

To set the gain quickly on your Infinity amp - put in a disc that you like that has some good rockin music on it - no Celine.. Turn your amp gain all the way down and then your deck volume about 80% of the way up (turn off all the LOUD, Bass, Treble, etc). Now turn the gain up on the amp until either the speakers sound distorted or the clip light blinks on the heaviest beats.
done.

The gain meter is at the 7 o'clock position, and when the volume is at about 35 on my pioneer headunit, the clip meter starts to blink. Theres no way that the amp is sending 90 watts to each speaker. What could be the problem? Also, should I avoid using the "Loudness" settings?

set it as "DUKK" instructed. Use your loudness for tracks that need it, any amp will distort if the signal is over-boosted. If you set your gains properly as stated, it should sound good and relatively loud. Just as a note, 90 watts means nothing, a speaker that is very efficient/sensitive can sound just as loud as one that is not at half the power. If you had lower end speakers in there previously (they tend to be more sensitive), and you now have components or higher end co-axials, they may be the same loudness, though they will or should sound better.

^ x2 run with the Dukk for max SQ and max safe volume

Ok after I get the gain set, can I start to adjust the headunit settings such as mid, treble, EQ, etc. Also, is it ok if the amp clip light just blinks on the heavy notes or should it not be on at all?

first, thanks for the great explanation dukk. iv have been playing around with the gain on my 4 channel amp lately and i wasnt sure where exactly the optimial volume on the head unit should be. iv also been seeing my clip light come on a lot lately. i just put in a 12" clarion sub rated at 600rms i still have to check weather its wired to 4 ohms or 2, but for some reason my infinit 1211A mono amp which is rated at 1200rms has been flashing the cip light not constantly but pretty much at every beat in a good song. i know on some amps the clip light can be very sensitive.

yes you can adjust those after. Ideally, you shouldn't see the clip light on at all. That's why you use a dynamic music source such as pop with a track that's a little bass heavy. This will keep your maximum gain level within the safe limits should you choose to abuse your volume control. Keep in mind that not all sources are recorded at the same level, most newer pop/rap cd's are recorded at very high levels (even clipping on some tracks), so if you set your gains with an old cd from the 80's, you can easily get into clipping with new material. Use a music cd in the genre that you listen to the most, and try to choose one that has high recording levels (the one that you always have to turn down when you pop it in the deck because it's louder than everything else!).

I can tell when my fronts or rears are clippping, but i cant tell at all when my sub is cliping. Does this mean i have not even reached the clip level, or is it actually trickier to hear the clipping in it?

Try disconnecting the sub, and tune your cabin speakers, and when you are happy with the sound, leave it as is, and set up the sub output to match them, so everything blends nicely. You can try crossing the speakers at 80 hzs plus, and sub 70 htz and below. Not sure if you have a subsonic filter on the sub, if you do, place it at 30-40 htz. At these frequencies your speakers and sub should not work too hard, and you should be able to get better performance out of the amp, as it will not work as hard to try to reproduce anything lower than 30-40 htz, and that way all your other frequencies will get louder.