Best gain setting for my amps?

What's the logical way to set your gain control for your amp for best sound quality? I'm referring to my 4 channel amp powering my 4 speakers and my 2 channel amp bridged in mono. What do I listen for as I tune my system? I have my 4 MB Quart speakers running with the HPS switched on the amp. I have the 2 channel mono bridged at 800 watts into 2 - 12" Fosgate HE2 DVC woofers. I keep messing with the settings on my head unit and amps but I can't seem to find a "sweet spot".

I like Nasty Totoro's method here: http://totoro.efiregate.net/HTMLPages/Tuning/GainSetting/GainSetting.htm

Be sure to read the entire two pages of information.  If you don't understand something, he is pretty good at answering questions.  The test CD he offers for download is a VERY big file, but it helps make things easy if you are serious.  Good luck.

I went back to Car Toys today. The installer said he installed the antennas in the OEM subwoofer hole. That won't do. I suppose I could pull them out and mount them on the rear window myself? Why would I do that when I paid?

Chad was real cool about it and said to bring back tomorrow and he'll put the antennas on the rear window + re-ground to get rid of the whining. We'll do some testing to see if it's that Coustic amp. Besides the whining, the amp sounds pretty darn good with the MB Quart speakers. But that whining is unacceptable. I'm not spending this much money to hear that ghetto whine.

Thanks fb. You are a great help. I have the gain just below a 1/2 right now. I will turn it down to 1/4 as you say. What about the bass boost? What level should I have that at? I have it at a little past 1/2 way right now. It sounds pretty good but it will go into protection if I play some rap or something with a lot of continous, low bass. I want have it set so it doesn't go into protection at higher volume levels. You're right about these Ultimate amps, they're pretty sensitive to clipping. Should I keep this Ultimate amp to power my 2 - 12" Fosgate HE2 woofers or return it for a Kicker 800W amp? Is this a good amp to use mono bridged at 800 watts? I like the amp when it's pusing my woofers correctly. It sounds pretty clean.

I'm bringing my car back to Car Toys in about a hour from now to hopefully resolve the whining and mount the TV antennas (VHF and UHF antennas) to the rear window. Thanks for all your input. You're great!