about the md 1d is supposed to draw 90 amps at 1 ohm1200 rms but how many would it draw at 2 ohms 750 rms..im guessing about 55 -60 amps,i really wanna stay away from a ho alt,400 bucks is alot of money for one,and i believe 750 rms a be good enough for everyday listening,need to keep my hearing

Do you really plan to run around town with your system playing full tilt sine waves? Music is dynamic and estimating current draw will not really get you the answer you are looking for. A better question to pose would be to outline what other gear you have, how large your alternator currently is and ask what you should do to reinforce your electrical system to support it.