RE: Goldberg 40 cub
I have had good luck ordering electric flight supplies with HK. That being said they offer NO SERVICE on anything,and good luck should something be faulty.
[link=http://www.hobbyking.com/hobbyking/store/__9963__ZIPPY_Flightmax_5000mAh_4S1P_40C.html]LIPO[/link] 51.09
[link=http://www.hobbyking.com/hobbyking/store/__14405__Turnigy_G60_Brushless_Outrunner_400kv_60_ Glow_.html] Brushless .60[/link] 51.79
[link=http://www.hobbyking.com/hobbyking/store/__10331__Turnigy_Brushless_ESC_85A_w_5A_SBEC.html]ESC[/link] 36.59
It will at least give you the right idea. Everything listed here would fly the plane nicely if not a bit of overkill on power.
Gray Beard has the right of it however.