I've got the Godox PB960 Lithium Pack. It's well worth it vs. AA packs. Dual output and Li battery with a capacity of 1800 full power pops is pretty sweet. The best price I've found on ebay is $170, without flash specific cables. Both Adorama, B&H & Cheetah Stand have re-branded versions of this pack. Interestingly the price varies widely based on where you get it. The B&H rebranded Cyclone DR PP-400DR is 2x that of the Godox or Cheetah Stand version, while the Adorama BP-960 only carries about a $50 premium.
The thing is if you add up the total cost of ownership of AA packs (chargers, decent AA rechargeables, and the packs themselves) you get very close to the cost of the Godox that is superior in every way. I can use mine on several shoots before it even drops to 50%.
More info found here if you're interested:
http://flashhavoc.com/godox-pb960-lithium-power-pack-review/