I too need to replace chargers.

I'm in the US.

Anyone have recommendations for a good charger for these 4x1650 battery packs, also will they work with the 4x2650 or the 6x1650?

While I'm at it, one battery pack is discharging faster, need longer runtime anyway.
Is it better to get 6x1650 or 4x2650? And are some better then others? If so any recommended?