Subs stop hitting when volume and gain are turned up?

Check these sites out...it is a good reference. http://www.bcae1.com/ http://www.termpro.com/articles/articles.html#How If your headlight dims with the bass notes, the “BIG 3” might work. If not an H.O. alternator will be needed, or else be prepared to pour a lot of $$$ for batteries. This site explains the "BIG 3" upgrades. http://www.sounddomain.com/ubbthreads.php/ubb/showflat/Number/312025/page/1

Well the first problem is you're running 600w of power on a 300w amplifier. When you turn the gain up, it still doesn't power the subs enough at all, and it overheats very quickly and shuts off in protection mode. Get a larger amp, and make sure it powers the subs correctly at the right ohm stability. Keep the gain down a little bit so no overheating occurs and you will be all set.