Can I drive two Cinema 30" displays from a MacBook Pro (Retina)? I've used a "Mini DisplayPort to Dual-Link DVI Adapter" to drive a single Cinema 30 from my (2014-era) MacBookPro11,2 before.  Can I hook up two of them to drive a pair of Cinema 30's?  It's got 2 Thunderbolt ports and 2 USB ports, but the USB are on opposite sides -- will the USB cable reach?  (UPDATE: The cable will reach, but it's pretty tight.  I wouldn't want to plug/unplug it a lot.)

Is the USB plug just for power, in which case, could I plug it into a different USB port?  Or is it needed for extra data, too?

Alternatively, is there a Thunderbolt dock that supports this?  The docks I've looked at so far say they don't support multiple displays, but they seem to assume a new Thunderbolt display, so it's not clear.  Dual-link DVI is kind of an odd beast.
The USB cable is only for the ports in the back of the display.  If you don't intend on using them, you don't need to plug it in.  

USB 2.0 has a max cable length limit of about 5 meters.  You could get an extension cable that keeps you below that limit and it should make things work smoothly.