i have a 2000 honda civic and the batterry is like 410 cca. alternator is pretty small. i have a 1.25 cap and a directed 1100d mono amp. i was looking into getting an optima battery but the only gel battery made for my car is from interstate and it is a yellow top. so should i run a secondary battery in the trunk or get a bigger battery and place one battery in trunk and illiminate the front battery. ( im sure i would have to upgrade alternator) but does anybody see a wiring problem from this. also if i run this at a 4 ohm load it will only be 475 rms. is that my safest bet on this car or should i upgrade.
If your alternator is too small then you have to get a bigger one. Adding a second battery will only let you play your system with the engine off for longer periods of time.
the amp is rated about 1072 rms at 1ohm load and 8o8 at 2 ohm load and about 476 at 4 ohm load. so i dont have any power windows but i do have an alarm. im woundering if this amp is gonna cause problems on my 75 amp alt.
It's too small. The amp alone will draw over 100 amps of current at full output. Even at a higher impedance, the amp will pull a good bit of current, remember that when impedance is dropped (say you're running at 2 ohms instead of 4) the voltage and current raise because of less resistance, so in essence, an amp running 475W at 4 ohms will pull more current than a comparable amp running 475 at 2 ohms. Alternator is the best bet, like Wahl said, batteries only help when the car is off. You also have to consider than even if that amp pulls 50-60 amps, you have to have enough reserve left to run the computer, ignition, power windows, lights, CD player, A/C or heater, etc.
By the way, deep cycle batteries suck for starting cars. Cranking amps aren't a huge issue for starting a Honda 4-banger, but the only benefit of a deep cycle is additional amp-hours for when the alternator isn't charging (aka when the car is off). Stick with a wet cell and a good alternator for the best results and simplest wiring.