I can highly recommend 4x18650 Coolook PB-2000.
I bought 2 from Fasttech. My android tablet and phones, my iPod, all Apple devices I tried charges great with this unit. My friends are using it when they come over and it newer fails to charge. It charges my picky Galaxy Tab 7.7 with same current as original Samsung charger. It can supply more that 2A without problems. By the way, I’m using some old laptop pulls in the power bank and I’m sure it’ll be even better with nice new batteries. Another thing I like is that battery voltages are nicely balanced when discharging. That’s not the case with some 3x18650 ENB power banks I’ve had. HKJ tested this power bank some times ago, here’s the review: Review: USB battery box 4x18650 Coolook PB-2000