| i want to put in two 1000 watt subs plus speakers |
What? New mid+high speakers or are you talking about sub drivers? The speakers themselves don't draw power, it's the amp, telling us the speaker wattage (and not even specifying peak or RMS) doesnít help us too much.
If you get a 2000W amp (which you donít need, since the sub rating you gave is probably peak. Peak rating is a marketing term and should be ignored) then you are going to need a 1-2 farad capacitor into your car's electrical system to act as a buffer to ease the strain on essentially ALL of your car's electrical components. Massive voltage drops (which occur when you play hard bass notes on a weak electrical system, seen as light dimming) are hell on modern electrical equipment such as microprocessors and such. Either way, anything that produces more than 1kW, you need at least a 1 farad capacitor per kW of drain that you have.
If you have an 80 amp alternator, you MAY be alright with a big enough capacitor. Anything less, I'd get a new one (might as well get a badass one while your at it). I agree with El Presidente. Just get one big alternator.
Now, so I can really give you specific directions on what you need to do, tell me what kind of amplifier(s) you intend on using, the drivers you plan on hooking up to them, and your listening habits. (Loud? Bassy music? Both?)
What I need to hear from you: What kind of driver is it? What is the RMS rating on the subs? DVC? Ohms?
Do you have an amplifier? List it's specs [such as THD, channel separation, signal to noise, RMS wattage]) If not, what do you plan on getting and list it's specs. Plan on getting it all professionally installed or are you more of a DIY in this field? What kind of enclosure is the sub going to be in? (let me tell you right now, do not get plexi glass OR lexan.)