Nissan quest alternator in s14
 

Is it really a big difference?

Reason I ask is because I have number of problem in electrical power

1. Turning on my headlights, rpms drop then rise
2. Subwoofer (cheap amp and 10inch), causes too much stress on my electrical equipment
3. Anything else turned on, rpms drop still.

Ever since I got the car it's always been doing that.

Question is, will the quest alternator help in this situation

Probably will. I have one for sale.

Get a farad capacitor while your at it.

was the cheap amp and sub in the car when you bought it? if so remove it/disconnect it all and see if it changes, if the cheap audio system Did do damage to the electrical system your problems may continue even after disconnecting the audio setup. get out the FSM and your muti/ohm meter and start checking your wiring.