You have good detail in the outer nebula, but the central portion is washed out. Try masking the highlights and using the detail from the shorter exposures to build your composite. You can get more help on the APML (Astrophotography Maillist) which I highly recommend. M42 should have some blue in it, but E200 doesn't capture it well.
Taras
P.S. Most of my photos are taken in the Catskills, though I have made a few attempts in the city. My web site has an M42 photo taken from my roof in NYC http://homepage.mac.com/tarashnat/astrophoto/0004-26.html in a one minute exposure.