Yeah, it will kill your alternator eventually. I had a new one put in years ago, before I worked on cars, and they wouldn't warranty it because the Audio system was installed.
Even a 1/2 farad will help a lot, the rating of 750 watts is like absolute peak power, chances are you are running way lower than that, and thus a 1 farad capacitor is overkill. But it's up to you. Just do it asap, and just don't go to full bumpage until you do, it's hard on your car in general. You will always have worse gas mileage with the system on, anything electrical puts strain on the alternator, and increase the drag on your engine...
Jung