Mikey, save your money and get The Best controller. I have one and it is well worth the money. Get that first and then the Atari Max. Not only do you get the gold plated contacts for the buttons, but you also get the extra tactile feed back from the new fire buttons. They are so easy to press and hold to activate, you wont get hand cramps when playing for a period of time. It's worth the money, literally silky smoooth!
But as far as the different power supplies between the 2 and 4 port models, I have to say that I own both a 2 and 4 port model and only 1 power supply and my single power supply works with both. Have never had any problems in my experience. YMMV, just enjoy the games and the nostalgia! Also, get a trackball if you can THEY ARE AWESOME!!