Video Calibration?

I own a 55" Mitsubishi WS-809 RP. tv and I picked up the Avia hometheater set up dvd.Now,after using the video calibration test patterns I thought the picture was terrible except for the 480p display on dvd and even that could use some improvment.What I did after a few days of these new settings was switched every thing back to standard setting and used my IRIS control witch controls the contrast and brightness automatically,according to the brightness in the room.I read in alot of hometheater mags that calibration is a must but after I did it my self with this Avia dvd I was scratching my head wondering why the picture was so poor.I also hear of ISF a technician who comes to your house and calibrates your set.Has anyone ever had this done and if so did it make an improvment?I heard you can have it done for about 350.00.Im happy with the picture now but if I can get more out of my set for a reasonable price I will.