Batteries and charger dilemma

Hello,
 I'm brand new to this RC flying thing. Just purchased a used Easystar
and discovered the 6 cell 7.2v NiCad batteries, even after cycling
several times, will only give me about 3.5 minutes at full throttle.
Now I suppose new battery packs are in order but I'm uncertain in
which direction I should head. I have an older AstroFlight charger
that will only do NiCads and the Hitec charger that came with the
Easystar that will only do NiCads. So, do I buy a few inexpensive
NiCad packs to get me off the ground and use my current chargers or do
I go for NiMh packs and purchase a NiMh charger or go all the way with
LiPo and a LiPo charger?

Tom in NJ