To replace a 3 cell lipo pack you really need to go to a 4 cell 123 pack. The full charged cell voltage for a lipo is 4.2v and the fully charged 123 cell is a little over 3.6v. So you need 4 cells to get the voltage up. Amps are no problem with the 123 cells as that is their strong point, but the cells are also heavier and take up more room so that is the negative side of the 123's. On RCG guys are ordering on E-Bay from a company called Toolking and paying $6-$7 dollars a cell (the 2300ma size) in the DeWalt power pack and then you have to tear it apart and make your flight packs.
I have only use the Black & Decker 1100ma sized 123 cells, but have had great service from them as 2 cell RX packs and also as 4 cell power packs in my planes. They are more rugged than lipos as you can over discharge them and charge them at high amp levels and they just keep on keeping on!!!!!!


Good Luck
Bob