Best native resolution possible: 640x480 through RGB SCART or VGA. Use RGB for games that don't natively support VGA mode. Or use the trick method for VGA... I moved my Dreamcast to my PC and set up a VGA splitter for inputs and audio to my kickass sound system. Talk about massive baselines from machinery and such in game. Poor grandparents. They're 300' away and can hear it from time to time...
I think the SCART cable does not support 480p, max 480i however... Only the VGA box would support 480p...
^ Ah. I wouldn't know since I'm in the US and use composite, S video, Component, or VGA. Even with a cheap $20 (USD) VGA box from FleaBay my video comes out extremely good on my 1600x900 VGA panel.
If 1080p is a requirement, use an emulator. If you want the best 480p you can get: https://www.facebook.com/Cabous.Dreamcast.VGA.cables. A bit expensive but great quality. Else for cheaper VGA cables, look on ebay/amazon.
