The DocKtor often gets asked for ideas on how to connect more than three monitors (in addition to the one native to the PC and two native to the dock). Most application requests are for four external monitors, and some as many as six. By connecting one Targus USB3.0 SuperSpeed Dual Video Adaptor model number ACA039US ($99.99 SRP) to one of the Targus Universal Docking Station USB3.0 ports, and additional two monitors can be connected (VGA, DIV-D, HDMI) for a total of five (including the PC native display). By connecting a second ACA039US two more monitors are added, and so on.
The picture below shows and example with five external monitors connected to a Surface Pro 2 using the Targus ACA039US and ACP71.
As of the DisplayLink v.7.6 software, there is no limit as to how many external monitors can be connected. The only limitation is in the performance of the PC. That is, eventually, you may find that the PC's graphics adapter cannot handle more than about six external displays effectively. The DocKtor has also noticed that at about six external monitors, its gets confusing as to where the mouse is :-) For those of you only needing the external functionality provided by two external monitors, the ACA039US can be plugged into a local USB port on the PC (with no dock needed). And if you only need one external monitor, consider the ACA038US ($79.99 SRP).
These two devices are very handy in conference room applications. The user needs only to connect the USB cable to their PC with the monitor end being connected to the projector. This is most certainly preferred to hunting around for an adaptor for the PC video out port to the projector/TV video input port. Note, the DocKtor most often recommends the ACA039 for this application because its HDMI port also has 5.1 audio on it. The DocKtor is OUT.