First, when you say a "modern" sega cab, you need to be a little more specific. Is it the Virtua Tennis 2 style? (metal frame tilted slightly back?) Or a japenese sitdown cab? The point being the monitor that comes with some of these accept VGA (31.5khz). And I do not know if it will also accept std res (15khz)...which you will only be able to output from a PS2.
Lastly, it would be a disgrace to not use this with a Dreamcast. Not only because its a real Sega cab, but also because the Dreamcast can output both 15khz and 31.5lhz.
