i wonder if my 3500d would be happy with 2 of these's??? Well I can say that I have a shit stock alt, generic starting battery, and a single d1200 in the rear, with a saz3000d. Gain is set relatively low but I can still hammer on it with somewhat decent voltage. If you plan on upgrading alts then between the new alt and two of them, you'd probably be good. (assuming your not playing very long / loud with the car off). If no new h/o alt, then they may not be enough. Do you know what amperage your stock alt can produce? yeah when its running i get voltage drop but thats after playing for a little, and i do plan on upgrading my alt next friday when i get paid to a 270 amp alt. my stock alt is 130 amps. was thinking maybe trying to get a bracket made so i could keep stop and have another alt to help out further. and then haveing 2 of these in the back i think i might be good.