M17 runs slow when lid closed

I've got a 27" external display for my Alienware M17.  The problem is, if I shut the lid on the laptop, it switches to a new profile, (affecting color settings and text magnification), which is good, but it also runs horribly slowly.  The display stutters, horribly even if you do something as simple as dragging a window.  Performance is absolutely horrible, and playing a game would be impossible.

I know that there's some curious arrangement at work whereby the video data from the NVidia card is passed through the Intel adapter prior to display on the local screen.  In fact, the Nvidia adapter doesn't directly affect the display at all when I'm using the laptop monitor, and the Nvidia Control Panel is disabled.

Is it possible that the Intel adapter is being disabled when the lid is closed?

This is annoying, because performance is horrible on a secondary display with the laptop lid closed, but if I open the laptop lid, the secondary display uses the color profile and settings (ICM file and Intel color profile) from the laptop, instead of using the correct calibration for the external monitor.

What am I doing wrong?  Is there a magic setting I can toggle that will fix performance?