Try to avoid buying a bunch of LiPo from China when possible. Shipping is pricey, and 'capacity' based, not weight.
The 4S hardcase packs from the US warehouse are the best deal. Spend $100 or something like that, and shipping is $0.01! Compare that to the $100-400 in shipping alone for a bunch of those from the HK warehouse.
Theyre OOS right now, and no telling when stuff comes back in... If you really need or want the stuff now, the Turnigy 6S 20C 5AH LiPo is probably the best bet. Find someone who recently purchased one or more, and get a buddy code from them. If you can't do this, buy one yourself from a new account, and use the buddy code to buy the remainder on your normal account. Its $42.88 or something like that with the buddy code. Get a bunch to make shipping a penny, and you have a cost effective solution.
Be sure to use code mili09 at checkout to save 1%. They kind of hide the place to enter codes, be on the lookout.