i just got 4 packs of a123 batteries (and their charger) and love them! i bought their charger, but i also had 2 Ice chargers. i sold one, and plan to sell the other as soon as i get get a castle BEC to replace my ni-mh rx pack. anyhow... 30-40 minutes is a long runtime, lol. build (or buy) your packs in a 2p configuration. you'll still probably only see about 15 minutes of runtime with a 9xl, but since you get a discount - buy an extra pair to swap out when the first set runs out.
if you're using the Ice and balancer, you'll need a lipo-dapter.