For those viewing this thread who may want information on setting amplifier gains, this link is useful:
http://www.bcae1.com/gaincon2.htm
That is a great site Carl - it can be a bit "daunting" to go through it all but the site is like the "Prego" ad ..
If you'd like to learn more about mobile audio ... "It's in there!"
JL Audio is one of the most obsessive companys I've dealt with when it comes to SQ. They really are fanatical about it. Here is the JL Audio method for adjusting gains:
http://mobile.jlaudio.com/pdfs/gainSetting.pdfCombine the "bcae1" site with the refined method from JL Audio (if you'd like to get that precise) and I would think a given system would be about as spot on as possible. Always keep in mind that adjusting gains on an amp is about getting the best performance out of an audio system. It's like putting your amps on a dyno

If there was any way possible I would have installed an MHD400/4 on the bike - alas - just 1.5" width too big. The procedure laid out is not for the impatient, but is one of the best. Even if you don't plan on going through it to this detail it's still a good read to help understand the goal.