a123system batt and charger

has anyone tried these yet? im interested in the combo that comes with two batterys and charger , i think they are 2300 mah batts , about $175 so the price is right but i dont know if it is better to go with a higher voltage, these packs are 6.6 volts so it would be 13.2 volts in a revo with hvmaxx 4.5 system . any thoughts or suggestions would be great , thanks