haha i know man. trust me, it is bothering me too!! i have a camera and will take some pics when it stops raining. and i looked at the big 3 i did under the hood and i think that the grond off the battery is on a painted surface?? could this be a contributing factor? my ground from the amp is the best (cant get better) drilled through my floor and bolted directly to the frame! ill get some pics posted! i also gotta work though. ill try to get them up before i go to work...
ya that is a major contributing factor. all your grounds need to be on bare metal. you want it scrapped until its shinny as hell. make sure it's fairly flat too, if there's a bunch of deep grooves from scratching it down too much then there'll be poor surface contact. get the paint in that area its touching clean, i recommend buying a cheap wire brush at home depot.
2 most important things right now besides fixing your crappy grounds are a battery for that amp, and a new HU. You should get something rated at at least 4v for the preamp voltage. i recommend alpine, eclipse, or pioneer.
as far as mixing batteries....there's a catch. you're SUPPOSED to have only the same kind (AGM, deep cycle, etc) and have them the same age. When they are differant kind of batteries, one of the batteries which isnt as charged as well will pull charge off the more charged battery. For a temporary setup, this isnt an issue, its when you have them like this for months itll start to harm the batteries over. for the time being get an hc2400 for the trunk, and after you get a new HU, get the front battery replaced with an hc600 or 800. if you reallllly cant afford a smaller battery for up gront, you can get either a battery isolator, or a solenoid. a battery isolator will direct the charge to one battery at a time, and a solenoid will disconnect the connection between the 2 amps when the car is off. i like solenoids more personally.....these things will range from about 30-50 bucks i think for a 300amp one. you can do one of these, but IMO you're better off with a new battery up front later on
when you scrap these grounds, the amp will be probly be able to pull more even though your preamp voltage is shitty. you NEEEED to get that 2400 for the trunk or else you run the risk of blowing your alty or amp trying to run that amp hard on an inadequate electrical.