>> broadcast DVD quality.

Broadcase quality and DVD quality are two distinct things. The FCC has technical specification for what can be considered broadcast quality.

Some consider BQ to be anything above 30 fps at 800x600.

Broadcase quality generally refers to TV. Low res TV systems use a 4.2 MHz bandwidth with 525 to 625 lines per frame (USA). Then there's medium res and HDTV (8 MHz or more of bandwidth).

If that's what you are looking to do check out Avid. For systems like that - you can't build them yourself. You'll need to use an Avid approved Xeon workstation (usually from Fujitsu Siemens/HP). Or you will have no end of headaches.

RT.X100 is severely underkill. If going with Matrox you will need a Digisuite setup.