Do I really need to upgrade my alternator before I add my car system ?

I have a 2007 Impala LS and I was told that I need to change my alternator first..Another person told me I could just use a second battery such as optima so my battery won't die..My entire car stereo system is 1200 watts and I don't want to mess up anything..
Do I really need to upgrade my alternator before I add my car system ?
look at you amplifier/s and note the fuses installed. check the radio fuse . Now add up the value of the fuses. then check the current rating of the alternator. you've said the system rating was 1200w then at 12 you will require 100amps max to run the audio system. assuming these figures are accurate then your current alternator [ probably 60 to 80 amp] will not suffice. I asked you to add up the vale of the fuses because this gives a more realistic view of the current required. If the 100amps is correct then you have no reserve current available to run the car or charge the battery;therefore you will be required to upgrade your alternator. ps if you never run your system to near its capacity then you may just get away with not upgrading the alternator. But if you intend to drive it hard then you will need to upgrade or you will suffer endless flat batteries and reduced performance from your motor vehicle. good luck.
Do I really need to upgrade my alternator before I add my car system ?
It would be advisable, however not absolutely necessary. You definitely should get a second battery, and have an Optima or something other than stock under the hood as well. Kinetic or XS Power are the two more known brands for Car Audio batteries. You can put one in the trunk, but BE SURE TO SECURE IT!