These are the receiver batteries I use 2,000mah 4.8V with a U connector (start buying everything with U connectors, U=universal and will work with any brand)
http://www3.towerhobbies.com/cgi-bin...&I=LXNRH6&P=ML
All-Battery.com has transmitter batteries 2300mah for $16, I don't know how good they are but I have bought other batteries from them in the past with good results.
http://www.all-battery.com/index.asp...S&Category=165
Switching to Sub C or NiMh doesn't matter except Sub C will be heavier and really no benifit. NiMh in AA is plenty.