In a nutshell, the 550 has the following edges over the ATI 200 theater chip:
1) Theater 550 boards are now coupled with the MT2050, which adds tuner support for SECAM, DAVIC, DVB-C, DOCSIS 1.0 to 2.0 and EuroDOCSIS.
2) The chip itself now performs the MPG2 A/V encode functionality so capturing/recording is done by the chip rather than CPU. This saves CPU effort while capturing or recording.
3) The 550 has a 5-line comb filter and a full frame comb filter (touted 3D comb filter) which can sharpen text, clear video noise and improve video quality.
4) The 550 has Digital A/V synchronization circuitry for processing audio which keeps A/V sync'd properly. It uses the PCI bus versus dongle/bypass cabling to your soundcard. This should completely eliminate out-of-sync audio to video of previous combination cards.
