If you are playing out in the street/parking lot or your club does not have a hard case requirement you can't go wrong with the following.
Turnigy nano-tech 5000mah 6S 45~90C Lipo Pack
Turnigy nano-tech 5000mah 4S 45~90C Lipo Pack
Most roar racing or club events are restricted to 4S battery power with hardcase. The most reasonable offering is from Gen Ace they will not break your bank.
Gens ace 5000MAH 14.8V 40C Lipo Battery Pack
Unlimited funds go for the Thunder Power hardcase G6 lipo.
Have had the best luck with EC5 or 5mm bullet connectors. Deans/Traxxas connectors will not stand up to the abuse if dragracing or high speed runs.