I have a 99 honda civic Dx automatic and my alternator isnt supplying enough amps for my system. I went to autozone to get my alternator checked just to get the specs and its only supplying 70 amps and 12.7 volts. I have coaxle speakers and an amp supplying 300 watts for all 4 speakers(total) Rms. In addition, I have a sub and an amp for that, that is running about 1000 watts rms. From what I have looked up on car audio magazine they show me the formula for calculating the amount of amps needed to run my 2 amps and system; which is the following formula : divide the Rms power rating of of each amp by the amount of voltage my cars electrical system will produce. (coaxle speakers and amp) 300 watts Rms/ 12.7 volts = 23.62 amps, and (sub and amp) 1000 watts Rms /12.7 volts = 78.74 amps. In total My system needs 102.36 amps ( not including the amps my car needs to start and run all the other things like fans, ac, head lights etc.) im not sure how to calculate that but I have heard it is around 60 amps needed . (In total 162.36 amps are needed to run everything fine/safe)
      Finally, leading to my question, do I need just one alternator supplying 170-180 amps or should I get dual alternators to solve my problem. Also, what would be the pricing for each solution. I Read about some guys problem similar to mine on a forum and What does it mean when he says that on a higher amperage alternator, hes sacraficing voltage for more amps; he also says that when the car is at idle the voltage drops below 12. Is there a way around this( any tweaking to the pulleys).  

have you checked into a dual battery isolater? stinger and other co,carry them that and two optimas,a cap or two on the amps might do it.but back to the original question,loo into a local trucking or oilfield service shop.if your willing to fab,they run up to 250 amps or so,yea big n heavy too.
umm...jacobs make a "accuvolt"jobbie that raises the amps going to your powerplants,higher voltage less amps to drive the amps.
look in jegs,com and there are  volt batterys that drop down to  when running down.luck to ya,hope you can use some of the ideas  

alright
dude try the big 3 upgrade. it helps save all the volts going thru the car.
in addition with that i would get a decent cheap alt.
that would help solve your problem you will have enough power for a couple tv,s too :P