2000 watt system questions

[MECHMAN]

Ok so right now I have my amp set up around 1200 watts, at 1000 watts solid on the amp there is 0 notice in lights or anything, when I start pushing 1200 point you can see minor dimming starting. I'm about to run 2000w rms to my 2 apline type rs and I wanted to know what would be the most cost efficient change to do to keep my car from dieing and what not. Thanks in advance. The current alternator is 80 amps. Its running no capacitor and has a single battery.

Update:

In the m3 the battery is mounted in the trunk in a sealed off compartment, The subwoofers take up pretty much the whole trunk so I dont really have any place to add a new battery at all =/ Would replacing the current battery with a much better 1 and replacing alternator with a 140 amp alternator solve my problems or not really? And is it worth it to add a capacitor?

I would start with a battery upgrade and the big 3. Which will be tough since it is in the trunk But you will see some improvement in the vehicle charging system.

I would rather add a small secondary battery way before I would use a capacitor