Critique my System Please

I would use a 2 guage power wire for the amps

yea, 2 gauge wire, to a distributoin block, then go 4 gauge from there. when you say hatchback sub enclosure box, do you mean the loaded boxes with the tweeters and mids in there, or just an angled sealed box?1990 Honda Civic HB:

Clarion DXZ545MP H.U.

2- 6.5" Power Acoustik interiors

Diamond Audio 600.1 amp

Diamond Audio 15" M6MKII

Pyramid PB881X 4 CH. Amp

 The old battery should be fine, but if you have a stock alternator it probably won't be up to the task. The link you refer to for the subs says they are the dual 2 ohm version, so your wiring choices are 8, 2, or 1/2 ohm at the amp. Assuming you will run it at 2 ohms, this amp will be pushing 600 watts. The other amp,  assuming you run it at a 4 ohm load will be pushing around 300 watts (all assuming that Audiobahn's ratings are close to actual power.) You're looking at 900 watts- you'll need about 144 amps from the alternator. This is more than most stock alts. even produce. Have a look at your stock alt. and try to find the amperage rating.  Multiply that # by 60% (roughly the amount of amps needed for the cars basic electical system.) Whatever is left over is what is available for the stereo or any other electrical add-on doo-dads.  (Example: 100A  alt. = 60A for car, 40 left for stereo.) Keep in mind though that you won't want to push the alt. to it's full capacity all the time.  The only solution is to buy an aftermarket high amp alternator with enough power to cover it all, with a little room to spare. I know, it sucks. I recently realized the same problem during my first big wattage build. There are several good aftermarket alts. out there.You'd better get me out of this lord... or else you'll have me to deal with. -- Hunter S. Thompson "F.A.L.I.L.V."