RE: Giant Scale Batteries
A123 is a brand name for LIFe batteries. They were one of the first available so the "A123" has stuck as THE NAME, like Kleenex. Some still believe thay are the best and only to buy, but as time goes by, more and more LiFe are becoming available, GP's Life series for example. SO if you want A123, buy Life's (Lithium Iron Phosphate) from some one. But, note that you will also need to buy a LiFe compatible charger.
BTW, a personal opinion moment. I don't believe that the type of battery you buy and use matters as much as your technique for using them . If you develope a good regiment for maintaning and testing your battery, then the type, LiFe, Nicd, Nmhd, doesn't matter. They will all work.