electrical components?

Definitely upgrade the big 3, this will help in any case.  The most critical part of an auto electrical system is the alternator.  This is what produces the power used by the car and by all the electronics including any stereo system you add.  The battery is to start the car.  A cap is to maintain momentary peak output of an amplifier during a burst or transient, but only if the alternator can supply enough power to recharge it.  Bottom line is if you are using under-drive pulleys you may already be at the capacity of your alt just running the vehicle.  Adding an amplifier (and let's not forget the weight of a subwoofer system) will most likely counteract the small HP gain you get by using the pulley, even if you install a higher-output alternator, so it might just be a wash anyway.  Plus HO alts tend to need to spin faster than standard alts to produce usable power.   I suggest simply returning to the standard pulleys first if you want to include a large subwoofer system, then decide if you need a larger alt.Support the12volt.com