electrical system in 04 impala.

Hello all, I have a 2004 Chevrolet Imapala and need suggestions on what to do to get my current system fully powered. My lights dim extremely bad, and I feel like my amp is clipping way to easily. -Details- HU: KDC-X794 AMP: JBL GTO 1201.1 II *~1200W RMS @ 2Ohm* (Gain is set to around 1/3 of a turn, still get lights dimming. Don't have a good multi to measure voltage sorry.) CAP: RF 1-Farad (got it for free..) Alt: GM Stock (120Amp max) Bat: Interstate Megatron II Front Doors: Alpine SPS-600 6-3/4" Rear Deck: Stock 6x9 (open to upgrade ideas) Cable size from bat to amp: 4 Gage Ground: Used dremel tool on trunk body, 4 Gage Subwoofers: Two RE SE-X 12" 4Ohm, wired to 2 Ohm (600W RMS single, 1200W RMS Total) Box: L port 4-Cubes @ 33Hz I don't have a ton of money to dump into my car at the moment, and what I have now is from months of saving. What would the next few steps be to get this car fully powered and sounding clean? I know I will need to do the big 3, but will I need a new alt too? Any recommendations for new 6x9s?

Using the rough rule that current input = power output/10 = 1200W/10 = 120A, so your alternator may not be too small. Whilst your alternator wonl't always be putting out its max of 120A, you are probably unlikely to be putting out 1200W RMS for long. But it is a balance of average alternator output versus average amp consumption PLUS the normal vehicle loads like lights, ignition, and battery recharging. The best indicator is a voltmeter across your battery so you can get a feel for when you are discharging the battery as opposed to the alternator supplying the load. The Big 3 may solve the dimming. A bigger alt may solve the dimming. Power redistribution may solve the dimming. Otherwise a 2nd battery (AGM) at the amp may solve the dimming, else across the lights. A cap across the amp or lights may likewise solve the dimming, but a small AGM battery is usually cheaper and better - it depends on the battery and amp size and their dynamic response.