12 volt batteries will not give you 17 volts unless you have a means of charging them up that high and keeping them there and I would strongly recomend that you save up and upgrade to a 16 volt system if you plan to run at 17 volts. those 12 volt batts will not hold up long charged that high.
first you will have to upgrade all of your electrical you will need one or more alt. with an external regulater that can go up to 18 volts you have to have 16 volt batts and then you have to run a kick down so you dont fry the computer in the car.
you can get 16 volt batts but if you cant charge them to 16 volts they are useless. you either have to spend cash on equipment that will run well at 12 volts or else spend the cash on a charging system.
wtf lol if you do not know that i would imagine you do not need to be running a 16 volt setup..
your alt now is set to produce around 12 volts so if you got a 16 volt battery setup you would be charging them only up to 12 volts.
you will need multiple 8 volt battery's wired in series i believe to get 16 volts.
and i doubt your cars electrical could handle 12 volts so you would need to isolate your batterys from the car and have the rest of the car run off 12 volts and your stereo run of 16 volts..