Before:
... <key>SHOWFULLNAME</key> <true/> <key>lastUser</key> <string>loggedIn</string> <key>lastUserName</key> ...After:
... <key>SHOWFULLNAME</key> <true/> <key>autoLoginUser</key> <string>>console</string> <key>lastUser</key> <string>Restart</string> <key>lastUserName</key> ...Notice the extra ">" in the line with "console" in it (this is to pass ">console" as the login user name). Now reboot, and you will never get the GUI at bootup. It's command line only from that point forward. If you want to go back, edit the file again, and remove those two lines, and reboot.
[robg adds: This seems like a much easier way of disabling the GUI than the method discussed in a previous hint, though I'll admit I don't understand all the nuances of the differences between the two.]

