Or get a DVI to HDMI cable and use FCP’s Digital Cinema Preview. This will send your video out full screen to the second monitor connected to your computer.
I don’t really trust this option for color at all, but if you just want to see the video bigger, it’s a good option.

-Russ
Russell Lasson
Colorist/Digital Cinema Specialist
Color Mill
Salt Lake City, UT
http://www.colormill.net