RGB capture cards are AFAIK only available for industrial purposes (=very pricey).
A very easy way to get near RGB quality through SVideo:
- get a decent Supervideo genlock (my Hama 292 was 8€, it's OK but not great)
- get a PVR card with hardware compression, use only highest bitrate (my Hauppage PVR PCI was ~15€)
or a DV bridge and capture through Firewire (marginally better quality)
or use the VideoIn of your graphics card (quality varies widely depending on hardware/driver/CPU speed)
- convert to MPEG-2/lower bitrate with a decent software compression, I like TMPGEnc a lot.
I wouldn't recommend converting directly to DVD rate MPEG-2: consumer hardware generates numerous artifacts, esp. when dealing with high contrast/hard edges video like the one you're likely to capture here.