Video Editing from MBP to multiple screens

you could use some thing like:
http://www.matrox.com/graphics/en/products/gxm/dh2go/
http://www.matrox.com/graphics/en/products/gxm/th2go/
to split the video output signal across two monitors.
Far as your computer is concerned both external displays is the same display. There are some important details. Like the displays need to be the exact same size. it's best to read up fully about them before using such a device.

Or you could get a USB to DVI adapter to hook up an extra display.
http://www.trittontechnologies.com/index.php/products/usbvideotechnology/see2-xtreme-uv200/

the splitter would probable give you better performance. but the usb would probable work more like having a 3rd display.

you may also want to consider one large external display.