this is my ride!

....Dual Plettenberg BigMAXXimum's with Schulze 18.97 esc's
I am going lipo...is this my best way to spend $700 more bucks?
a)2x MaxAmps 5000mah 4s lipo batts @ $193=$386
b)Hyperion Ballancer/Charger 0610i DUO @ $269
c)TOTAL= $655
Do i need anything else?...IE;plugs,wires,lipo stuff,etc?
Thanks in advance for the help!!!!