I always use a Travel Agent for vacations. Usually you get the best possible price or at least what you would have gotten if you'd booked directly. Two big reasons why I use them:
1) Saves time.
2) If something goes wrong they have much more leverage than you or I do. Plus they know whom to call to get problems fixed quickly.

I do all my research on the web, find the best rates and lodging, call my travel agent and she has always beaten my price or matched it.
Make sure they are reputable, for instance if they say, "where's that?" call another one.