Or like I mentioned already, can easily get USB to HDMI
Yeah but then it's using a tiny GPU on the USB adapter...and not really necessary if he already has outputs on the laptop/dock for DisplayPort. Might as well use the GPU power the laptop already has rather than try to output through USB. The DP->HDMI adapters will be much cheaper than USB video adapters as well.
http://www.amazon.com/Cable-Matters...424451364&sr=8-2&keywords=displayport+to+hdmi
My friend had bought a USB video adapter so he could have more monitors at work on his laptop than it would support...and it was around $60 or so for 1 (if I remember correctly).