I found a 5V 4A power supply on ebay that should drive these things up to warp speed on ebay. Not sure how long this link will be valid. If it's dead, just google "5v 4a power supply", or what ever you're looking for.

Don't expect your hubs to power 7 miners on 3 amps of power! 3.5 amps is needed for 7 hubs, perferabaly 4 amps.

http://www.ebay.com/itm/5V-4A-AC-DC-Power-Supply-Replacement-Adapter-with-2-1mm-x-5-5mm-Tip-Center-/220960385060

been using this one on 70 sticks with HW errors around 1%. The cheap 10 port hubs are actually mining with 10 ports http://www.ebay.com/itm/-GENSSI-5V-40A-200W-Regulated-Switching-Power-Supply-FAST-FREE-SHIPPING-USA-/171123409781